Moves that make the user faint when they use the move.
The moves that will OHKO the user without fail are as follows:
Explosion Final Gambit Healing Wish Lunar Dance Memento Misty Explosion Self-Destruct
Perish Song will make the user faint if it does not switch out by the time its countdown reaches zero.
Moves that cause the user to faint (Bulbapedia)