Can anyone please tell me the best way to kill a person? Poison or anything else? Please let me know!

My bro is a phycho! My parents are afraid of him!

He hits them, swears them, threatens them, robs their money and does everything possible to hurt them! We sleep hiding in a room at night scared that he will come to kill us! We cried so much and that’s it! Not anymore! I want him dead!

*PS: we tried counselling, phychiatrist, meds, relatives, friends, neighbours, cops, advices, requests, weeping, begging, fighting back and
IT DIDN’T WORK!!