About Donflamingo. Sure his DF ability seems to be very powerful, but we still know very little about it. Like how it really works and on what people. There will surely be some kind of limitation to it, because I doubt he can just control other strong people with it.
And that he has the highest bounty ever doesn't mean much. It could simply mean that he was a pirate a long time before he joined the WG.
Just look at Blackbeard, his bounty isn't very high because he joined the WG so fast.
I'm not saying that he isn't strong. He is a Shichibukai so he should be. I'm just saying that we can't really put him into a strenght listing with so little information.
We pretty much can't do that with a lot of informations. Those listing never really work because it all depens on who fights who.
"For Feanor was made the mightiest in all parts of body and mind, in valour, in endurance, in beauty, in understanding, in skill, in strength and subtlety alike, of all the Children of Illuvatar, and a bright flame was in him"