I don't know maybe it is the way he took advantage of victor when he was sick. The way he made his sister lie for him over owning Jabot. The way he moved up the memorial service for his father so Gloria would miss it, in fact the way he decided his father's funeral would be the way he wanted and to heck with everyone else.
The way he took advantage of his own father when he was not in his right mind, to have John change his will leaving Gloria nothing, having no respect for his father's wishes.
The way he reacted years ago when he found out Jill was pregnant with Billy.
The way he blames everyone and anyone for his mistakes instead of taking responsibility for them.
The way he went against his father's wishes about taking Jabot public because he thought he knew so much more about business than his father which resulted in the family losing the company in the first place.
The way he treated Nikki and Phyllis when he first came to them about the spa idea, then bringing an injunction against them to try and keep them from starting the business.
His smug "it's my way or the highway attitude."
I could go on, but I am tired of typing about him, :)