Gunslinger Ally: Deadly.
Card sounds may differ from in-game as they get updated.
Deadly - Units and spells with Deadly kill any unit they damage, regardless of health. For example, a 1/1 with Deadly can kill a 5/5 attacker.
Ally - Happens as soon as you have a unit of the named type. This can be when you play the unit with Ally or later if there's none of the needed type in play. Ally resets if the unit dies or is returned to hand.