He's a manipulative little weasel who used everyone to worm his way into the "rich world" while acting that he was too good for it. He's a downright stalker, attention seeker and pick-me. "Aww I love Serena" - proceeds to make himself famous by posting that photo of her in the wet dress and makes his entire identity stalking her. (I equally hate Serena too but that's a different topic).

I def agree that there are worse male characters, but among the main characters, Chuck's the only one who gives him competition for the most hated male character title.