What's the worst thing you have ever done to your best friend?

I’m probably gonna get a lot of hate for this, but fucking his ex-girlfriend very soon after they broke up.

It turns out he didn’t care because he was already fucking another girl afterwards too. So oddly enough we bonded even more.

Slapped them for killing my wife

I feel like I should take some responsibility for my best friend's 2:2 at uni, when she was predicted for a 2:1. All those times I invited her over to play video games didn't help.

Ghosted them.

Didn't need the racist toxicity in my life.

Left them for college and made new friends.

I had a fling with his gf. I was young and she was hot, he doesn't like me that much anymore.

Edit x gf.