Advice, please?

Take him back, but this time, be really clingy, bratty and everything he hates. That should make him back off.

... do the only sensible thing....

schlagen, punsch him in the face and run >,...,<

Hm sorry for asking this but why do Du hate him Du should at least give him a chance:)

Ahhhhh the old 'i Liebe Du I Liebe Du not' I've sort of been there just tell him Du hate him and that Du really mean it don't threat oder anything but yeah tell him that Du two are just not meant to be togather and that Du don't wanna ever be togather with him ever again and if he still comes at Du say something similar to what Du did but make sure Du say it in a calm serious firm tonewhere if Du just yell at him he'll just think your joking oder something

Well, obviously, this guy is a biscuit. To deal with biscuits, Du need to just ignore the living crap outta him. he will leave Du alone.

Tell him that you'll never get back together with him. If he asks why,tell him that Du don't want a boy who cheats on Du and calls Du a slut. Get him out of your life.

Tell him that Du hate him and if he doesn't leave Du alone you'll drop a heavy metal Piano on his head.