There wasn't really a "moment" when I realized it. Just a gradually building frustration with him and everything he does. Just some examples
Whenever there's a problem (especially one he caused), he will literally say "not my problem" and/or "not my fault"
He constantly starts arguments, just for the sake of arguing and causing stress
There was a period where he'd let everyone know he is an atheist.
He's always the victim
Has absolutely no concept of manners. Literally said that they're a pointless construct of human civilization.
Does not stop pushing his perverted furry shit on people
Frequently does mean things and then frames them as jokes, and then proceeds to ask why you can't take jokes
Can't take jokes himself
Throws other people under the bus to save his own ass
He has a counter argument for every argument he has used against you in one of his forced pointless arguments. Refuses to accept this when it's pointed out.
I have to keep being this asshole's friend until high school ends. Drama with him will be far worse than being a fake friend for another year. He used to be a good person.