As long as it's your turn, Spiteful Prankster has first strike.
Whenever another creature dies, Spiteful Prankster deals 1 damage to target player or planeswalker.
If another creature dies at the same time as Spiteful Prankster, Spiteful Prankster’s last ability triggers for that creature.
If your life total is brought to 0 or less at the same time that a creature is dealt lethal damage, you lose the game before Spiteful Prankster’s ability goes on the stack.