I'm going to indirectly call my friend/coworker ugly
Why do you want to call him ugly?
He's been a bad, boring and very ugly person who has been acting like a rude to me.
I'm sorry that your friend/coworker has been acting rude, but you shouldn't talk about them behind their back. Also, if this person is actually a friend, you shouldn't insult them. Instead, try talking to them about how they have been acting.
He is being a bad friend to me
I understand but you are being a bad friend by talking behind their back too. You should sit down and confront this issue with them.