I'm going to ignore an ex-good friend of mine.
Why are you going to ignore them?
I'm fed up with his behavior. He thinks he can get away with everything, you know?
Even though you two aren't good friends anymore you shouldn't ignore him. Don't be rude, at least greet him politely.
It's not possible for me to politely greet a person  who is not respectful to me. It is a fact that he is a manipulative piece of shit.
It can be  hard to be nice or polite to someone who has hurt us. But you will be seen as rude if you ignore somebody in a social situation.