Sturdy

Introduced in Generation III

When this Pokémon is at full HP, any hit that would knock it out will instead leave it with 1 HP. Regardless of its current HP, it is also immune to the one-hit KO moves: Fissure, Guillotine, Horn Drill, and Sheer Cold. If this Pokémon is holding a Focus Sash, this ability takes precedence and the item will not be consumed.

“The Pokémon cannot be knocked out by a single hit as long as its HP is full. One-hit KO moves will also fail to knock it out.”

As a regular ability 39

As a hidden ability 8