Dan Scott is without a doubt the worst character on the show. He started out as a bad father to Lucas and a manipulative man, but ended up being a murderer and literally a villain.
he murdered his own brother, Dan dated Karen back when they were in high school. He abandoned her when she got pregnant with Lucas and was dating Deb just a few months later and got her pregnant with Nathan. He was truly the worst boyfriend, and character, on the entire show. Even though the show tries to give him somewhat of a redemption arc at the end, it was hard to take seriously.