deadly laughter

1: Laughing so hard, it could kill you.

2: Laughing so hard that it hurts.
3: Laughing so hard that you feel you are going to die, can't breath, etc. Ex: Hearing the best joke ever.

4: A sinister laugh that is full of evil. ex: A cackling witch
5: Laughter that is lifeless and does not sound happy.

"The witch gave the deadliest laughter when she cackled."
"Never tell a zombie a joke, it will give the most deadly laughter you have ever heard."
"After telling the joke, the room was full of deadly laughter."
"That emo stoner girl has the most deadly laughter when she hears a joke. It freaks me out."
"I nearly died from laughter when I heard the punch line."