The basic principle is that whenever you kill an enemy, all damage exceeding their remaining hit points will be added to the next gunshot.
To avoid confusion, here are some terms:
- Excess Kill: The first kill which will leave behind excess damage.
- Excess Damage: The excess damage left from the Excess Kill that will be added to the next shot.
- Overkill Shot: That next shot will get increased damage from Excess Damage.
Overkill Damage: The *overall* damage of the Overkill Shot.
What counts as Excess Kill
The Excess Kill can be a gunshot, a grenade, a melee attack, or an action skill attack… doesn’t really matter, what counts is that it’s the last kill.
What counts as Overkill Shot
Only gunshots (including rocket launchers etc., everything that’s in your gun slots). Damage of melee attacks, grenades, action skills etc. is not increased by Overkill. You can melee and throw grenades, as long as they don’t *kill* another enemy this will be ignored for Overkill. Excess Damage is preserved for the next *gunshot*. Note I’m saying *shot*, not *hit*. If the gunshot misses, Excess Damage is gone.
You can also wait a long time, reload, switch weapons, travel between maps, etc., Excess Damage won’t be lost until you fire the next shot or quit the game.
Overkill “stacks” in the sense that with a more powerful Overkill Shot, you may kill an enemy leaving even more Excess Damage, then kill the next enemy with an even more powerful Overkill Shot which will leave even more Excess Damage, etc. until you hit the Damage Cap.
Excess Damage Calculation
ExcessDMG = DamageDealt - HitPointsLeft
This is simple enough. The Excess Damage which will be added to the next shot is the number that pops up on the kill minus the hit points the enemy had left. Element and enemy type doesn’t matter because that’s already covered by DamageDealt — it’s simply the number popping up.
Naturally, you don’t know the exact number of hit points left (health amounts for test subjects were determined), it’s a visual estimate then. Less health left = more Excess Damage. There are a few special cases to consider:
- Multiple projectiles: When killing an enemy with a multi-projectile weapon (e.g. a shotgun), no more projectiles will hit the enemy than needed to kill them. If e.g. they have 160 health left and you’ve got a shotgun that does 100×5 damage, only 2 pellets will hit them even if they’re standing right in front of you. Examples with this enemy:
100×5 shotgun: DamageDealt = 2 × 100 = 200 >>> [color=44ff44]ExcessDMG[/color] = 200 - 160 = 40
250×2 Q-System: DamageDealt = 1 × 250 >>> ExcessDMG = 250 - 160 = 90
500(×1) sniper: DamageDealt = 500 >>> ExcessDMG = 500 - 160 = 340
Generally, ExcessDMG cannot exceed the damage of a single projectile. The higher the damage of a single projectile, the better for ExcessDMG — which mostly favors single-projectile weapons.
What if you kill several enemies with one hit, e.g. with a rocket? The game won’t add the Excess Damage of all enemies together, instead, it will just take the Excess Damage of one of them. I don’t know how it decides which enemy to pick for this.
If an enemy is killed by a damage over time effect such as burning, only the last bit of damage that finished them (again, the last number popping up) will be used for Excess Damage calculation, which usually won’t be much.
Overkill Damage Calculation
On the next shot, your Excess Damage will be added to the gun’s *base damage* — before all other bonuses are applied.
OverkillDmg = (BaseDmg + ExcessDmg) × GunDmgBonuses × ElementDmg × CritDmg × ...
For example, let’s say our gun has 1000 base damage, Excess damage is 2500, and we’ve got +30% from Personal Space and +20% from Wrath, and it’s fire vs. flesh (× 175%):
OverkillDmg = (1000 + 2500) × (1 + 0.3) × (1 + 0.2) × 1.75 = 9555
Since Excess Damage received all the same bonuses that the base gun damage did, in principle our overall damage was increased by +250% because Excess Damage was 2.5 × base damage.
There’s one exception to this: amp shields. These only boost base gun damage, not Excess Damage. For example, if we add a Re-Router (+120%), we will get (1000 × 2.2 + 2500) = 4700 (before the other bonuses are applied).
Excess damage will be distributed evenly among the projectiles (for n pellets, it will be ×1/n for each pellet). This only applies to regular multi-projectile weapons that have “XY×n” gun damage on the card — special weapons that have multiple projectiles without the “×n” mentioned under gun damage (e.g. Bekah, Lyuda) will have full Overkill Damage on every projectile, greatly increasing their Overkill potential.
Overkill can’t be exploited infinitely, there is a maximum damage cap based on the weapon’s gun damage (that’s the gun used for Overkill Shot, not the weapon used for Excess Kill) — so forget using 50k excess damage with a level 20 gun, that won’t work.
For single projectile weapons it is +400% damage:
OverkillMaxDMG = NormalDMG × 5
However, multi-projectile weapons suffer a severe penalty:
OverkillMaxDMG = NormalDMG × (1 + 4/n)
Where n is the number of projectiles. A Q-System (2 bullets) will have max. +200% damage, a 4-pellet shotgun max. +100%, and a 16-pellet shotgun max. +25%. This e.g. means that the Maggie is crap for overkill: being a 6-pellet weapon, it gets max. +67% — while an ordinary Ranger pistol gets max. +400%. As above, this does not apply to Bekah, Lyuda etc. — they have max. +400% on every pellet.
Even though amp shields don’t increase Excess Damage, they do increase the damage cap: the 1000 dmg gun from the previous example is normally capped at 1000 × 5 = 5000 (before other bonuses are applied), but with the Re-router the cap rises to 1000 × 2.2 × 5 = 11000.
The amp anointment (shield capacity added as damage to next shot after shield break) is added to base damage just like Overkill, but it also increases the cap: if the Re-Router has 15000 capacity, the cap will now be (1000 × 2.2 + 15000) × 5 = 86000.
There’s no difference in critical hit calculation, except that instead of NormalDMG× CritModifiers it’s now OverkillDMG × CritModifiers. This means that not only regular damage but also Excess Damage is multiplied, greatly increasing Overkill Damage potential. An Unforgiven does over 10× damage on crits, this will also apply to all the Excess Damage – but you’ll quickly run into the cap because of its low gun damage.
A ricocheting bullet has no damage penalty, so both enemies will each receive the full package (although the second one won’t be critted most of the time). Headsplosion and Pa’s Rifle can apply it up to 4 times. A Bekah theoretically up to 8 times!
Note about the Excess Kill: If you kill an enemy with a crit and the bullet ricochets to another one without killing them, Excess Damage for the next shot is based on the kill. If the second enemy is killed too, *that* will be used for Excess Damage. This means that if you’re unlucky, you do a feckton of damage on the first enemy but Excess Damage may be tiny because the ricocheting bullet killed another enemy.
Damage over time status effects are affected by Overkill too. The way this works is that damage is increased by the same ratio as the shot itself:
OverkillStatusEffectDMG = NormalStatusEffectDMG × OverkillDMG / NormalDMG
Killing an enemy with a gun or action skill creates an orb that seeks out another enemy and damages them — dealing overkill damage with a small splash radius (but without the gun damage Guardian Rank).
RemnantDMG = (RemnantBaseDMG + ExcessDMG) × Element
Where RemnantBaseDMG is the damage stated on Remnant’s card (651 at level 50).
Edit: Remnant receives more bonuses than that, it receives a lot of bonuses actually — action skill bonuses, splash damage bonuses, elemental damage bonuses, and so on. Now Remnant is something that’s really painful to test — just know it deals a LOT of damage. It regularly deals millions of damage, it easily deals dozens of millions of damage, it sometimes deals 100s of millions of damage and sometimes it exceeds a billion. All with only one point. Just put one point there and enjoy.
One important difference is that it has no damage cap — it can deal millions of damage with only one point invested. Raising base damage by adding more points becomes irrelevant with some good excess damage (and without, it does little damage anyway): if the orb does “only” 100k damage, two more points will only add another 1300 on top of that. So don’t waste points, 1/3 is all you need.
Interaction with Overkill Guardian reward
These two are mostly independent of each other. Think of it like this: you kill an enemy, and an orb rises. The orb carries Excess Damage from the kill which it will release on hit, but you also carry the same Excess Damage which you will release on the next gunshot. If you one-shot the next enemy, the (usually higher) Excess Damage from that kill will be carried by both you and the new orb rising from that.
Each orb keeps the Excess Damage from its respective kill, so if both orbs from the example are still in the air, they will do different damage on hit.
The most notable interaction is that if an orb kills an enemy, *your* Excess Damage will now be based on that kill, because the Overkill Guardian reward is always based on the last kill, regardless of what did the kill.
Hollow Point (Guardian reward)
This makes an enemy explode if they’re killed with a critical hit, damaging nearby enemies.
This is another instance of Overkill damage: The explosion’s base damage equals the Excess Damage from the kill. It is always non-elemental.
HollowPointDMG = ExcessDMG × ExplosionModifiers
Where ExplosionModifiers are splash/area-of-effect bonuses, e.g. from Arm(s) Deal.
Interaction with Remnant and the Overkill Guardian reward
Remnant and Hollow Point are completely independent of each other. On a critical kill, explosion and orb will both have the same Excess Damage, not influencing each other in any way. However, if the Hollow Point explosion kills another enemy, no new Remnant orb will spawn from that.
The interaction with the Overkill Guardian reward: similar to what Remnant does, the same Excess Damage used by the explosion is carried by you for your next gunshot. If the explosion kills another enemy, *that* kill is now used for Excess Damage on the next shot.
So with all three together, you’ll get an explosion based on the kill’s Excess Damage, an orb based on the kill’s Excess Damage — and your next gunshot will be an Overkill shot with the same Excess Damage unless another enemy is killed in the meantime.
(e.g. +100% damage after action skill end or +300% damage after Phaseslam) synergise very well with Overkill, similar to crit or charge bonuses. Like those, more damage on kill means more Excess Damage, and on the Overkill Shot they multiply all Excess Damage along with normal damage. Especially Amara’s +250% after Phasecast and +300% after Phaseslam anointments synergize extremely well with Overkill.
Bonus elemental damage anointments
(e.g. +20% bonus Radiation damage or +50% bonus cryo damage) synergize equally well on the Overkill Shot, and all their damage is increased accordingly.
However, for building up Excess Damage they don’t work as well as the damage-multiplying ones, because similar to multi-pellet weapons they don’t deal more damage than is needed to kill the enemy. They’re in fact applied one after another, and when the enemy dies, the remaining ones are dropped and don’t contribute to Excess Damage. Thus, Excess Damage can never be more than the instance of damage that killed the enemy.
This also applies to bonus elemental damage from skills like Moze’s Cloud of Lead or Amara’s Forceful Expression — or most notably, Infusion which actually causes problems for Overkill (see the Notable Skills section).
If you’ve got several bonuses of the same element (e.g. you can have 4 fire bonus instances going on at the same time with Infusion, Forceful Expression, and a bonus fire damage gun and grenade): even though their damage is all added together in one number popping up, they’re actually applied one after the other in the same way as different elements. So on a kill, you may (in this case, likely) see a smaller damage number popping up, and the dropped instances again don’t contribute to Excess Damage.
Notable Weapons & Gear
This is far from exhaustive, just a few things I’ve tested with reliable results. I will add more once I’ve done more tests.
Alt fire mode spawns a flying gun shooting at enemies. Overkill damage is applied to *all* its bullets until it disappears.
The projectile reflects between enemies, *dealing Overkill damage on every hit*. Packs of enemies just evaporate even on Mayhem 4. It also deals a feckton of DOT. This weapon is insane by default, but it’s even more insane with Overkill.
Guns with excessive critical hit damage greatly improve Overkill Damage potential, because they turn little base damage into a lot of crit damage, which also applies to Excess Damage. For example, I have a +432% Unforgiven and a Jakobs sniper with ~3900 gun damage and +21% crit damage. They deal almost the same crit damage (15K) and they do 77K/78K at the Overkill damage cap. The big difference is that the sniper needs about 17,800 Excess Damage to reach the cap while the Unforgiven only needs 4,800. In most cases, killing an enemy with the Unforgiven (regular damage) will instantly hit the damage cap on the next shot.
This pistol does about × 10 damage on critical hits (depending on parts). The best I’ve ever found is +432%. Sadly, it’s not easy to crit with it because it’s pretty inaccurate and usually doesn’t even have a scope. It’s pretty, uhm, hit and miss.
Shooting while aiming through the scope multiplies crit dmg by × 3.5 (hip shooting does regular crit dmg). Kind of the opposite of the Unforgiven since its excessive zoom level makes it hard to target anything that’s not very far away.
“Hidden” multi-projectile weapons
As stated above, weapons that shoot multiple projectiles without “×n” mentioned will apply full Overkill Damage on every projectile.
Four projectiles. Being a Jakobs weapon, each of the bullets can ricochet to another enemy on crits, so full Overkill Damage may theoretically apply to 8 hits (although that’s highly unlikely).
Some Maliwan weapons are able to multiply the entire damage dealt beyond what’s stated on the card, also greatly increasing Overkill potential. If you compare a 3000 dmg Jakobs sniper to a 1500 dmg weapon of this type that can multiply damage by 2, Overkill Max Damage will be the same but the latter will only need half the Excess Damage to reach it. Maliwan weapons always come with elements, so they can even deal much more damage than that Jakobs sniper.
Uncharged, this Maliwan sniper rifle does normal damage based on the stats on the card. Fully charged, it will do 2x damage (both impact and DOT), and on top of that it does splash damage — while still using only one ammo. Great for Overkill.
The pistol version of the Proton Rifle. Same effects, but since it’s got lower damage and lacks the sniper rifle crit dmg bonus, you’d probably prefer the Proton Rifle.
Even though it’s made by Vladof, this rocket launcher can be charged up for more damage, similar to Proton Rifle and Melter — except that it deals ×2.25 damage when fully charged. The interaction with Overkill is the same. With its monstrous damage, this weapon has extreme Overkill potential.
This alien-barrelled Maliwan sniper rifle is like an elemental railgun. What the item card doesn’t tell you is that *all* damage is multiplied by x2 (like a fully charged Proton Rifle, but the shot is instant). Gun damage, crit damage, status effect damage, Overkill damage, everything is x2. It deals massive status effect damage and hits multiple enemies if lined up, greatly increasing Overkill potential. Main downside: uses 3 ammo per shot.
Bolt and orb on their own each do damage based on the card stats. The combo however does a big explosion that can hit a whole pack of enemies, and it does x2.5 damage to every target hit, which also applies to Overkill damage.
Shotguns (or similar multi-pellet weapons)
These weapons are terrible for Overkill because they A) have low Excess Damage potential and B) suffer from the Damage Cap penalty mentioned in those sections above.
Maggie / Masher
Being basically shotgun pistols, these are very bad for Overkill.
While its damage can be increased a lot by both melee and other damage bonuses, its Overkill potential is very limited because of the 7 pellets. Excess damage can’t exceed the damage of one pellet and Overkill can’t increase its damage output by more than 57%. On top of that it can’t even crit, so this is a bad weapon for Overkill. Even with Amara with a lot of damage bonuses, it’s far from the Overkill damage some other weapons listed here can do.
These multiply NormalDMG, but not the ExcessDMG part. Thus, their damage increase is limited for OverkillDMG. However, since the damage cap is based on NormalDMG, they can significantly increase Overkill max damage. A Re-Router (+120%) increases Overkill max damage by x2.2.
Other Notable Skills
Far from exhaustive, I’ve only really tested a few so far.
Two F4ng (FL4K)
Somewhat problematic for Overkill. When procced, adds a projectile to the shot. This e.g. turns a 1000 dmg sniper into a 1000×2 sniper for this shot, triggering all penalties/disadvantages of multi-projectile weapons. If you’re chaining Overkill shots close to the damage cap, Two F4ng may be detrimental.
Ties That Bind (Amara)
It Synergises very well with Overkill. 35% of damage dealt to one of the chained enemies is dealt to every other one, and Overkill Damage increases damage to the other enemies accordingly.
Very problematic for Overkill. On the Overkill Shot, there’s no issue, all of it is multiplied. However, it causes problems for building up Excess Damage: since it divides the shot into two separate instances of damage, no more will hit the enemy than needed for the kill, similar to shotguns or bonus elemental anointments. If the 60% main damage is enough to kill the enemy, the 40% action skill element instance is dropped, reducing Excess Damage.
Example: 450 HP flesh enemy, 1000 Dmg non-elemental gun, no point in Infusion. Killing the enemy gives 1000 – 450 = 550 Excess Damage. Now add 5/5 Infusion, and the gun’s primary damage is reduced to 600, which is still enough to kill this enemy, resulting in 600 – 450 = 150 Excess Damage.
If the gun element and action skill element are the same, on hits you see only one number popping up with both instances added together, as if you weren’t using Infusion (60% + 40% = 100%). However, if the 60% instance is enough to kill the enemy, again the 40% one is dropped, resulting in the same loss of Excess Damage.