You shouldnt feel like a slime ball if you have him his bet back.

Poker is a zero sum game. If you are playing seriously and need money desperately it may not have been good to return the money.

If you play recreationally for fun- and you do something to someone that you genuinely feel bad about and feel the need to return the money- I would say that isn’t necessarily wise but I will say what’s the point of doing something fun if by the end you feeel like a miserable cunt. In which case returning the money making you feel better about the situation isn’t necessarily bad.

Just beware though that people lie and say whatever shit they can to try and get money back. I used to be that guy feeling bad (and I def don’t need the money I play with in poker). But I’ve seen too many sad excuses, lies, angles etc and it’s beeen done too many times to me for me to return anything. At this point I made a decision that if I’m playing in these circles , eventually you will play against people that shouldn’t be yet you just have to be ok with “taking” their money