I want it to be the Dragon Knight, because I have a connection with that character (having only played Divinity 2).
But it should probably be the Divine when all is said and done. For story reasons.
I can feel your pain, as my only experience has been with ED, prior to DKS. I'm afraid the story will likely let his holyness do the deed. Although, I would find mucho-mucho gratification in a personal slaughter of the Damn One. Something I have longed to do, after the depressing end of ED...
I need to fill that void and find some personal closure...