Touch Her and Die Trope

A protective or possessive hero warns anyone, often with a violent glare or threat, that harming the heroine will bring his full, merciless wrath. It's a declaration of ownership and devotion wrapped in menace.

Readers crave the rush of being so thoroughly claimed that any threat to them becomes a death sentence. It delivers a primal fantasy of absolute protection, where the hero's power exists solely to make the world safe for her.