If I remind my friend that he still owes me money ($275) from 2016 will that ruin a friendship?

He's not a real friend and I'm sure he knows that he owes you this money. Tell the sorry b astard that you want your money back. You don't need friends like that.

If he owes you that much money, he's not a friend anyway. He should have paid it back a long time ago. Ask him.

This is why i don't loan money to people.

Ask him if you can borrow $275 but never pay him back.

It might, but you really are friends, this person should have had the decency to have repaid you by now; and if you really are friends, this person will be embarrassed but will happily try to repay you now. If he gets angry and if it ruins your friendship, then this person never really was your friend.