Although the pop-up text shows "Crushing Hit" when it happens during combat, the in-game help describes Crushing Hits as "Fatal Blow" -
"Fatal Blow - Attacks with a fatal blow with a fixed chance if you don't get a critical hit when attacking with an advantageous attribute. The fatal blow inflicts 30% additional damage."
There are four types of hits that can occur:
- Glancing Hit: 30% less damage
- Normal Hit: 0% additional damage
- Crushing Hit: 30% additional damage
- Critical Hit: starts at 50% additional damage and goes up according to your Critical Damage value
See also: Hit Table
The most common situation when Crushing Hit might occur is when attacking with attribute advantage. This will give the attacker a small chance to Crush; but it still won't happen if one gets a glancing hit or a critical hit instead (This is most famously the case with Ifrit (Water) - Theomars. While his passive grants him attribute advantage whenever he attacks, he won't get a Crushing Hit if he gets a critical hit instead).
However, several monsters have a skill that guarantees a Crushing Hit. The following are the monsters with fixed Crushing Hit chances:
- Brownie Magician (Fire, Water, Light): "Fly Fly" (AoE Defense Break)
- Inferno (Wind) - Anduril: "Hell Blow" (ATB reduction)
- Phantom Thief (Water) - Luer: "Crime Alert" (AoE ATB reduction / Defense Break)
Arguably, the primary benefit of a guaranteed Crushing Hit is the prevention of a Glancing Hit, because the latter cannot apply debuffs.