Fear Roulette, a known Instant Death attack.

An Instant Death attack is a type of an attack that is mostly seen in Super Mario RPG: Legend of the Seven Stars.

As its name tells, the character on that is used dies instantly, no matter what is his or her HP, Defense, Magic Defense etc. There are no more than 5 of these in the game. An example of an attack is Jinx's Silver Bullet and Smithy's Tank Head's Magnum.