I had a moodswing and felt sad and suddenly I burst out crying because I felt sorry for how I always talking bad about this one anime character from ohshc.
You feel that way about a fictional person? Why do you think you feel so sad?
I feel sad because I can be so mean to this character
It is understandable why you would feel upset when you realize that you are being mean. It is normal to feel bad when you are not being nice. Stop being mean and you will feel better.
But I didn't want to make them feel worse by making fun of their anime. I didn't want to be a dick. Can't we all just let this slide?
Well it seems like you feel bad enough to stop doing it, so you probably can just let it slide. The good side to this is that it's a fictional person, so there's not even anyone to make amends with.