A critical hit has a certain chance of happening, default 5%, for each enemy hit by an attack. When it occurs, the attack causes additional damage (default +50%) and, if it kills the target, destroys its corpse. The animation of the latter effect depends on the type of damage dealt. For example, Holy damage may cause the target to be vaporized, while Physical damage can tear the victim limb from limb, and Cold damage can freeze the enemy solid, then shatter it, etc.
Whatever the case may be, its corpse cannot be revived by other monsters (like Fallen Shamans). Corpses that normally cause any on-death damage (Accursed noxious vapors, Molten explosion etc.) will not be destroyed, and the monster's post-mortem revenge will not be prevented.
Monsters cannot deliver critical hits: only the players can.
There are two stats that can enhance one's critical hits:
- Critical Hit Chance (granted by some skills, and also by items, normally rollable on gloves (up to +10%), rings (6%), bracers (6%), amulets (10%), helms (6%) and off-hand items (10%), +54% total. Some legendary items and class-specific items can roll critical hit chance as well (for all skills or for just one).
- Critical Hit Damage (granted by skills and items, normally gloves (up to +50%), amulets (+100%), and rings (50%), or +250% total, but some legendary items and can roll this stat on other slots). Emeralds in weapon sockets also increase CHD, by up to +130%, being the most used gem type for weapons in game.
For players who do wish to know each class's legitimate cap of Critical Hit Chance from items and skills (in addition to 5% innate chance), the list below sorts them out:
- Barbarian: 60% Critical Hit Chance (Battle Rage with Into The Fray stacks infinitely, Overpower with Killing Spree adds 8% for 5 seconds, Revenge with Best Served Cold adds 8% for 6 seconds, Wrath of the Berserker adds 10%, Weapons Master adds 5% for Mace and Axe weapons)
- Demon Hunter: 56% Critical Hit Chance (Sharpshooter passive skill can make it up to 100%, and additional 10% for Caltrops with Bait the Trap; Vault with Action Shot are guaranteed Critical Hits; with Archery, Hand Crossbows gain additional +5%; Single Out adds +25%; Wind Chill adds +8%)
- Monk: 58% Critical Hit Chance
- Crusader: 58% Critical Hit Chance (Judgment with Resolved effectively adds +8%; Bombardment with Annihilate rune will always deliver critical hits)
- Wizard: 58% Critical Hit Chance (Conflagration effectively adds another 6%, Energy Armor with Pinpoint Barrier adds 5%, and 10% temporary bonus from Frost Nova with Deep Freeze)
- Witch Doctor: 58%
In addition to those bonuses, Paragon levels can add up to +5% more critical hit chance and +50% critical hit damage. Shi Mizu's Haori and Broken Promises make all hits guaranteed Critical Hits on certain conditions.
Obviously, Critical Hit Chance is capped at 100% (achievable by legitimate means). Critical Hit Damage has no cap other than what is already allowed by skills, class, and equipment/Paragon levels.
An attack that delivered a critical hit is identified by damage numbers turning yellow and with larger font. Note that some Damage Over Time attacks may not roll Critical Hits. Instead, they receive a bonus to all damage dealt, the exact power of said bonus being a hero's Critical Hit Damage multiplied by his/her Critical Hit Chance. These same attacks may not trigger effects that require a critical hit to happen.