Don't forget to post some context for this interaction, such as who you were talking to, what you were talking about, do you want a serious or funny response?, etc.

you don't.

More context would be good. Personally I'd block them for fun. Seems like a good answer to "or what".

He said something agressive and I told him to chill he replied with or what. I didn't know what to say so I posted here

or your blood pressure will increase and youll have heart problems (you can try and exaggerate)/

Best comment i've gotten so far thanks man.

“Or you’ll join your friends on my block list”

Doesn't work dude is a stranger.

Or you’ll give yourself an aneurism and die so I win!