User blog comment:Raptor of Love/Flamingos Cards/@comment-4899461-20130227200336/@comment-4605926-20130307122721

I find it hard to see the connection between Doflamingo being Admiral level and the Spade Pirates not having any affiliation with him.

As for Doflamingo being Admiral level - as I already said here somewhere in the comments, we never saw Doflamingo injured in any way, nor did we see him fight seriously. That in itself is a remarkable feat which is to be feared of. In addition, we already know (kinda) that a Shichibukai can be Admiral level and perhaps beyond. Mihawk (who also shares Doflamingo's no-injury feat) is the strongest swordsman alive, he used to spare with Shanks, a Yonko. Also, don't forget that the Marines, Shichibukai and the Yonko are considered to be the "Three Great Powers" in the world. Therefore, while some Shichibukai may be considered a failure (Gekko Moriah) and some may seem weak in comparison (Crocodile), they're bound to be extraordinarily powerful. We've already seen in person that some Shichibukai are a great deal more powerful than others. Luffy managed to beat Crocodile eventually (due to unexplained methods though, since Crocodile was clearly supposed to be more powerful), while the whole crew didn't manage to even scratch Kuma in an all-out battle (on their side).

To sum it all up, the answer is inconclusive, both are extremely powerful, both were never seen fighting seriously, if you ask me, it could go either way. We're missing too many parts in the equation, as such, we cannot solve it and arguing about it would yield no results. You're underestimating the Shichibukai due to some prejudice but that isn't necessarily the case.