Time machine

You have a gun, one bullet, and a time machine that can only go backwards. Who do you kill?

(You)

Non-meme answer:Muhammad before he came into power.

Gotta go fast

Isaac Newton

Go back and kill God while he's busy creating the universe

stalin

Go back just before I step into the time machine and put a bullet in my fucking skull just like the fucker deserves, narrowly avoiding a paradox.

Soros (but only after he sold out his fellow Jews).

Maybe Rothschild or Rockefeller and try to get them lined up.

either caesar before the rubicon incident

or

anthony eden before the appeasement