What to do when you beat someone so badly that they don't want to be friends with you anymore?

Please give me pointers?

Hmm, I don't know. I'm sure it's more complicated than the way one game proceeded.

Why don't you show us the game?

DON'T over-react and write a blog post about it!
move on - who cares!

man you sound like someone who have no friend

Just ignore it and get on with life 

 I don't know... Beg them to excuse you.

You beg them not to unfriend you and desperately try to convince them that you're not that bad of a player and you were just having a bad day.

Haha, sounds good 

Never laugh at people whom you beat up in Chess.

I almost hated my friend who grinned  on me when he started winning his Chess game against me.

Everybody needs self-respect.

Beat them again lol