I think we can all agree that Bojack, as the main character, beats many if not all the main cast when we talk about being morally corrupted. Still, who have you considered a " worse person " — the definition of bad person isn’t really precise I know, but consider it as " person who does actions generally considered deplorable by the public. " — than Bojack while you were watching the show?
Joseph Sugarman who had his wife lobotomized after he recognized she had mental health issues and acknowledged he was too lazy to deal with them, blamed the Jews for “peeving off Hitler”, is implied to have sexually harassed his secretary and/or chested on his wife, and attempted to marry his only daughter off to a man she was not interested in to enhance his business interests. Joseph Sugarman has 0 redeeming qualities. He has 0 redeeming qualities and we don’t get any indication of addition or past abuse/neglect to explain his destructive behavior. The only character you could argue is worse would be Sarah Lynn’s stepfather, who is heavily implied to have sexually abused her.