Weyoun 5 just has so much sass. I mean he was the only one ballsy enough to flat out treat Gul Dukat like the batshit crazy son of a bitch he was.
Dukat was not amused by this of course, but tolerated it for the good of their allegiance with the Dominion. Deep down I think Dukat didn’t think he would ever achieve the greatness that he achieved during the Bajoran Occupation, and saw the Dominion as an opportunity to gain that power -and more- again.
Weyoun 5 was a character that just didn’t give a fuck. He knows that Dukat can’t kill him, that would put Cardassia’s partnership with the Dominion into question which was too much of a risk. Weyoun could be as snarky and have as much fun with his diplomacy as he wanted because he knew Dukat couldn’t do anything about it. Except cause transporter accidents but those are only small setbacks.
Bottom line? I fucking love Weyoun 5.