I don't care what you call it, if it ends in "ine" its good enough for me.

Strychnine

side note: It kills you by making all your muscles tense so strongly that you can't breath any more. The muscles in your face tense in a way that it gives you whats called a "Strychnine Smile".

>Strychnine Smile

Can also be caused by Tetanus

Or running for political office.

Or getting into a car accident: https://www.youtube.com/watch?v=NIbotIsLJWw

That's probably the botox. Deadliest known substance.