>>312
Castor oil beans
Costs around $5 for more than enough to kill a man.
Contains ricin, very dangerous in very small quantities.
8+ beans is considered dangerous to a human, get around ten, split them open and pour them into his soup. Do not eat any and handle them with disposable gloves. Remove the bean casings since they are largely inedible.
Fucker won't know what hit him, nor will anyone else for that matter.