A {{Stock RPG Spell|s}} whose damage is proportional to the target's current HP; the most common forms will reduce the opponent's HP by 1/4 (or 1/2) of its current value, weakening the target without killing it.

Like a FixedDamageAttack, these attacks ignore the game's usual damage calculations altogether, with the only variable being whether or not the attack actually ''hits'' the target to begin with.

Naturally, a character at full HP will receive the most raw damage, while characters with low HP will receive hardly any whatsoever. Whether or not this attack is capable of actually ''landing'' the killing blow varies by system: The amount of damage inflicted is typically rounded down, so a character reduced to their last HitPoint might receive no damage whatsoever (unless ScratchDamage is required, or if ElementalRockPaperScissors gives it a boost).

Sadly, most Percent Damage Attacks become a UselessUsefulSpell in the hands of the player: Despite that [[HealthDamageAsymmetry enemies have more HP than the heroes]] (meaning the attack can inflict greater damage), enemies will frequently evade the attack or simply be resistant to them ([[TheComputerIsACheatingBastard as a rule]]), and Bosses have ContractualBossImmunity against it or have large enough HP pool that any damage the spell does to them usually ends up being {{cap}}ped, meaning they're not any more effective than any other single-hit spell or attack that hits the cap as well.

An occasional variant is a FixedDamageAttack calculated using a percentage of the target's ''maximum'' HP, rather than their ''current'' HP.

Compare HPToOne, a more extreme attack that removes all ''but'' the last HitPoint from its target. If the damage percentage is 100% then you have a OneHitKill. Contrast RandomizedDamageAttack and SituationalDamageAttack.

!! Examples

!! Role-playing games
* The ''Franchise/FinalFantasy'' series has many examples and frequently classifies them as a "gravity" element, featuring versions that remove 25%, 50%, or 75% of the opponent's HP. Some can target multiple foes simultaneously, and are far more likely to succeed when used against your party members than against monsters.
** The Blood Sword of ''VideoGame/FinalFantasyII'' drains 1/16th of the target's max HP per hit, making it [[GameBreaker ridiculously powerful]] against bosses. Enemies' HP-draining physical attacks in the original Famicom version worked the same way.
** In ''VideoGame/FinalFantasyVII'', ContractualBossImmunity is avoided for some flying bosses, who only have a 50% damage reduction from it instead (including one of the two {{Bonus Boss}}es). Also, there is at least one enemy that ''absorbs'' gravity attacks as HP: Master Tonberry.
*** Some monsters in ''Final Fantasy VII'', including a mini-boss, are ''weak'' to gravity, which means that a 50% damage attack is effectively a one-hit kill if the monster's HP is less than the 9999 damage cap.
*** There is also one BossInMookClothing whose HP total is so high that gravity spells, while still effective, repeatedly hit the damage {{cap}} of 9999.
*** The FinalBoss has an attack with a spectacular animation that takes about two minutes to complete. It seems like an attack that should achieve an easy TotalPartyKill, but in fact all it does is take off 15/16 of each of your characters' current HP, so it's actually incapable of killing anyone.
** In ''VideoGame/FinalFantasyIX'' and ''VideoGame/FinalFantasyXII'', gravity-based damage is calculated based on an opponent's ''maximum'' HP rather than their ''current'' HP and therefore becomes a FixedDamageAttack.
** One of the first battles of ''VideoGame/FinalFantasyX'' involves an boss whose only attack is ''Demi'', which is a gravity-based attack that does damage equivalent to a quarter of each character's current HP. Anyone who knows Achilles and the Tortoise knows this boss can't possibly kill you with this attack alone. [[HotWitch Lulu]] (or anyone with the correct items and/or sufficient level grinding) can learn this spell later.
*** Several Sinspawn battles (particulary Gui and the power cores) use similar Gravity attacks. The most powerful ones pull out a much deadlier version called ''Gravija'', which cuts HP down to critical level, and then use an area-of-attack elemental spell to [[TotalPartyKill finish the job]].
** ''VideoGame/FinalFantasyX2'' has both flavors of percent-based attacks all over the place.
* In ''VideoGame/FinalFantasyCrystalChronicles'', the "Gravity" spell can be used once per battle against a few bosses to inflict a percentage of damage. It also temporarily immobilizes airborne opponents after damaging them, making them easier to defeat.
* ''VideoGame/BravelyDefault'' has Bone Crush, which deals damage equal to the difference between the user's maximum and current HP. If the targets are at full or near-full HP, they take ScratchDamage, while if they have half their remaining HP or less, it's a OneHitKill. You can get the spell yourself late in the game as BlueMagic (or the equivalent thereof). It also has Dark Breath, Dragon Breath, and Minus Strike, which are somewhere between this and FixedDamageAttack. Dragon Breath deals damage equal to the user's current HP, while the other two deal damage equal to the difference between the user's maximum and current HP. [[HealthDamageAsymmetry (Unfortunately for you, those two are also used by bosses....)]]
* In ''VideoGame/{{Persona 4}}'', while most Light element attacks are instant kills, one attack called "God's Judgement" reduces the target's current HP by half. Being part of the Light element, it can still be nullified/reflected by an appropriate Persona.
** In ''VideoGame/DigitalDevilSaga'', ''most'' Hama/Expel spells reduce HP by a percentage with a decent chance of working (both of those depending on the spell), but they will always hit enemies weak to them (Mudo/Death remains a OneHitKill).
* The "Super Fang" move in ''Franchise/{{Pokemon}}'' reduces the opponent's HP by half, and is mandated to inflict ScratchDamage if the opponent is already reduced to one HitPoint (which may not be what you want in a ''Pokemon'' game). It is not affected by the game's ElementalRockPaperScissors beyond the fact that "Ghost"-type opponents are immune to its element.
** "Nature's Madness", the signature move of the Tapus, is identical to Super Fang aside from being Fairy-type, a type nothing is immune to. The Tapus also have a signature [[LimitBreak Z-Move]], "Guardian of Alola", which reduces the target's health by 75%.
** The moves "Crush Grip" and "Wring Out" obey the standard damage formula (attack/defense power, ElementalRockPaperScissors, chances of a CriticalHit), but their base attack power is proportional to the opponent's percentage HP. If one strike reduced the opponent's HP by half, the next strike will only hit for half as much.
** In the ''VideoGame/PokemonMysteryDungeon'' spin-offs, collateral damage caused by [[ActionBomb "Selfdestruct" and "Explosion"]] is always 50% of the teammate's current HP (or if they are Fire-type, 25%).
* In ''VideoGame/SecretOfMana'' characters inflicted with "[[TakenForGranite Petrify]]" [[StandardStatusEffects status]] also lose 50% of their current HP as an immediate side effect.
** The Moon Godbeast Dolan in ''VideoGame/SeikenDensetsu3'' possesses an attack that reduces a party member's current HP by half.
* The Eclipse Dark Tome reduces the target's HP by half in ''[[VideoGame/FireEmblemElibe Fire Emblem: Blazing Sword]]'' and ''VideoGame/FireEmblemTheSacredStones''.
* In addition to various HPToOne attacks, ''VideoGame/ChronoTrigger'' features several bosses (mainly Dalton and his Golems) who use attacks that drop your health to half of its current state.
* ''VideoGame/{{Runescape}}'' has enchanted ruby bolts which have a chance to take away 20% of opponent's health from the enemy at the cost of decimating player's health. They're used to take down some of the stronger enemies.
* ''VideoGame/GoldenSun'''s summons use the target's max HP to calculate damage, but they also have a fixed base power.
* [[InvertedTrope Inverted]] in ''VideoGame/TalesOfMajEyal'': the Chronomancy spell "Echoes from the Past" deals damage equal to a percentage of the damage the target has already taken rather than how much HP it has left.
* Gnostic abilities in ''Videogame/TheLogomancer''. A 50% one is a reward for completing an early {{Sidequest}}, and one [[OneHitKill inflicting 100% damage]] can be learned by level up. (Certain enemies also have a variant that inflicts 99% damage.) Interestingly, [[ContractualBossImmunity bosses are not completely immune]], just heavily resistant, so they can still be useful against them.
* [[UniversalPoison Continuous Damage]] in ''VideoGame/SummonersWarSkyArena'' deals exactly 5% of the target's health per turn. Notably, it works on even the bosses, and is the only viable way to kill the [[DamageSpongeBoss Water Guardian]].
* ''VideoGame/LufiaIIRiseOfTheSinistrals'' and ''VideoGame/LufiaTheLegendReturns'' have [[LimitBreak IP attacks]] that do damage equal to a percentage of the target's current HP. Notably, they always avert ContractualBossImmunity and are typically necessary for overcoming otherwise {{Hopeless Boss Fight}}s or {{Time Limit Boss}}es.
* The ''Franchise/KingdomHearts'' games use the Gravity spells from ''Franchise/FinalFantasy'' as well with their strength being determined by how high Sora's max MP to remove a percentage of remaining HP from bosses, with the added benefit of also flattening enemies and leaving them unable to attack. Although [[ContractualBossImmunity most bosses are immune]] and [[spoiler: all Heartless will get an increase in defense after beating Hallow Bastion the first time.]]

!! Other genres
* The ''VideoGame/DungeonsAndDragons'' spell Harm is a 100% damage attack, which reduces the target to one hit point above zero (or 1 to 4 hp above zero in some versions), meaning the next hit that does damage will kill it.
* In the first ''VideoGame/{{Civilization}}'', nukes destroy ''exactly'' half of a town's current population, including defending units and one significant structure.
* The Sorceress in ''[[VideoGame/{{Diablo}} Diablo II]]'' has the Static Field skill, which does damage equal to 25% of target's current HP including bosses. Resistances and immunities apply. On Nightmare and Hell difficulties, this skill cannot reduce the health of enemies below 33% and 50% respectively. Against other players, it does only 4.375% damage after applying PvP damage reduction.
** The Crushing Blow item modifier provides a chance to reduce the HP of target monster, boss, or hostile player by 1/4, 1/8, and 1/10 respectively with each successful attack. This works with ranged attacks but the effect is halved.
* ''VideoGame/{{Worms}}" has the Battle Axe in some games, which halves the target's HP.
* In ''[[VideoGame/DeadlyRoomsOfDeath DROD]] RPG: Tendry's Tale'', stepping on a hot tile takes 5% of HP; stepping through an Aumtlich beam takes 50%. Optimisation often requires leaving healing potions untaken so your HP is low when you incur the percentage attacks, then taking them afterwards.
* ''VideoGame/DefenseOfTheAncients'' has Huskar's ultimate, named Life Break, which does this to [[CastFromHitPoints himself]] as well as his opponent, with the damage he takes being reduced as it's leveled up.
** Necrophos specializes in these kinds of attacks: ''Heartstopper Aura'' slowly drains away a small bit of health based on the target's max HP, and ''Reaper's Scythe'' deals extra damage based on missing HP, fitting with its status as a FinishingMove.
** This kind of damage, applied to a hero's right clicks, can make them a carry. Lifestealer's ''Feast'' lets him rip through opponents with high Str and/or items giving a lot of health, and Viper's ''Nethertoxin'', while increasing at set points, functions as a "damage increases as enemy HP decreases" effect that will quickly bring down anyone under 20% HP, since the damage scales exponentially and the bonus damage from only two attacks at that point deals about the same amount of damage as a standard nuke spell.
* In ''VideoGame/HeroesOfTheStorm'', heroes can choose to pick a talent that can deal this trope, most commonly being ''Giant Killer'' and its variants, which deal anywhere between 1.5% to 3% of the target's HitPoints as damage.
** [[VideoGame/DiabloIII Kharazim]] take this trope further. Kharazim can use one of of his two [[LimitBreak heroic abilities]], ''Seven-Sided Strike'', to deal 7% of the target's HitPoints as damage [[RuleOfSeven seven times]] to enemy heroes in an area.
** Meanwhile, [[VideoGame/DiabloIII Malthael]] is this trope taken to its LogicalExtreme. His trait, ''Reaper's Mark'', marks enemy non-structures he damages with basic attacks, causing them to take an additional ''2.5% of their max health'' in damage every second for 4 seconds. And one of his [[LimitBreak heroic abilities]], ''Last Rites'', is similar to Necrophos' ''Reaper's Scythe'' from ''VideoGame/Dota2''. ''Last Rites'' deals extra damage based on missing HP, making it a FinishingMove if the target has less than 33% of their max HitPoints remaining.
** What, no mention of [[Videogame/StarcraftII Tychus]]? His trait, ''Minigun'', causes him to deal 2.5% of the target's max HP per basic attack. Oh, did I forget to mention that he attacks four times per second by default (With a particular quest talent, this is taken up to five times per second), meaning that that is a whopping 10% of the opponent's max health gone per second by default. He also gets a variant of ''Giant Killer'' for one of his level 20 talents (Which, yes, ''does stack with Minigun''), and the ''Titan Grenade'' Talent applies this to his Frag Grenade, which makes it inflict 10% of the target's maximum health as extra damage.
* Pretty much a staple of ''VideoGame/LeagueOfLegends'' in several variations as below. Designed as a major tactical decision for a player, since percent damage works extremely well against characters with lots of HP but few other defenses, but is very ineffective against people with low HP that rely on healing or armor to defend themselves. Certain types of percent damage attacks are more common for certain archetypes:
** Damage set at a percent of target's current HP level, usually used by champions gearing up to kill HP tanks (e.g. Dr. Mundo's cleaver, Liandry's Torment).
** As a percentage of total HP, usually used for offensive spells to discourage buying HP in favour of resistances (With exception to Vayne, whose total HP based damage passive ability deals true damage and cannot be reduced).
** As a percentage of the caster's own HP, often owned by tank characters to encourage buying HP boosts (Sejuani, Shen)
** As a percentage of the target's missing HP and usually called an "execute", used by assassins (e.g. Kha'zix) to finish off foes one-on-one (damage increasing the longer the fight goes on instead of decreasing.)
** There is also percentage healing: Soraka's healing abilities are increased by 1% for every 2% of the resource the target is missing, Zac heals 4% of his maximum health if he collects the blobs shed by casting spells, and Dr. Mundo does both damage and healing by spending 20% of his current health to heal up to 60% of his maximum health.
* ''VideoGame/WarcraftIII'': The Death and Decay spell damages for 4% of a unit's total life per second, and lasts for 35 seconds.
** Several spells do percent ''buffing'': The Trueshot Aura increases ranged damage by 10, 20 and 30% (just 10 for the unit version), Roar gives all friendly units a temporary 25% damage increase, and Command Aura gives all units in range a 15% damage increase.
* Played with in ''VideoGame/TeamFortress2'', where the Spy's BackStab does damage equal to a certain percentage of the target's health--namely [[ThereIsNoKillLikeOverkill 200%]] of it. And it has a 100% chance to {{crit|icalHit}}, making the effective damage 600%. For most purposes this makes it indistinguishable from a OneHitKill, but in certain conditions (most notably using the Dead Ringer) the target may have enough damage reduction that can survive the hit.
* Several monsters in ''VideoGame/PuzzleAndDragons'' have percentage damage active skills, which take a percentage of the current health of all opponents, though these skills will have longer cooldowns at higher potencies. Several dungeon monsters have this among their attack, going as far as [[ThereIsNoKillLikeOverkill 1000%]], something that can only be tanked by either a damage nullifying active or stacking damage shield leader and active skills, and there are only a handful that can do that.
* ''OutpostDefenders'' has many items that deal a percent of the target's health. Usually, they are more expensive than other items, and they often only deal around 10% damage, making them only good for bosses.

!! Other
* The word "decimate" originates from a Roman military punishment, wherein soldiers found guilty of cowardice were ordered to draw lots, with one out of every ten[[note]] "decimus" is Latin for one-tenth[[/note]] men being executed as a result. The term is [[YouKeepUsingThatWord rarely used that way any more]].