For all of Bojack's flaws, he is still sometimes nice and he sees the wrong in his actions in the end, Velma doesn't even do that.

Yeah but Bojack's worst and most selfish actions, have much deeper consequences than Velma's. At worst she just loses a couple friends for awhile. Plus Velma lives in a toxic highschool environment, where everyone is selfish. Bojack lives in a similar state, but he's actively hurting people both mentally, and literally.

At least BoJack spends the entire series seeking redemption, Velma straight up doesn’t give a shit about anyone but herself.

She's also a teenager

Being a teenager and not give shit about others is not an excuse. Norville is in love with her and she laughs at his face and does not take him seriously. Plus, she is much more toxic compared to anyone in the show to the point no one not even the people in her school likes her.

Velma is Bojack but drained of everything sympathetic, self aware, or cool.

Are we just gonna ignore that Bojack's worst actions are far worse than anything Velma even considered doing?

Yeah, we're really going to do it.

This is matter of selfishness not heinousness.

Velma