Steal his girlfriend. She is your secret weapon.
(incase you fail at solution 1)
If you're sure that he is going to harm you physically, inform the police that you were threatened. Incase anything happens to you, the first person who goes to jail is him. Law pwns.
(incase you fail at all of the above)
Join the mob. No one touches the mob but the mob.
Go to Official DotA Website
> Heroes > Doom Bringer
Then click on his ultimate and click it on yourself.