Mystique snap neck with feet - X-Men 3 gif 1

In the third X-Men movie X-Men: The Last Stand, a captured Mystique (Rebecca Romijn) is handcuffed. The transport truck she's kept in is flipped, causing a guard to crash against her cell. Right as he recovers, she lifts her legs up, wraps one foot around his neck and pulls him closer to the cell, and presses the other foot against his face. Then she breaks his neck using her bare feet alone. "Told you so" she says mockingly. She takes the guard's keys using her toes and proceeds to unlock her handcuffs.

This scene further shows Mystique's talent for using her feet, being able to use them to break necks and unlock handcuffs with ease. Unsurprisingly, she quite enjoyed killing using her feet, and this definitely wasn't the first time she's done it.