Sakazuki alone would wipe the floor with all the living pirates. The only one alive that could maybe hold him back is Shanks. Add to that three Admirals, two Admiral candidates (Gion and Tokikake), Sengoku (retired but still alive) and we don't even know how powerful the "god's knights" are, having been introduced so late in the story, we can assume they are pretty powerful. Let's not forget the Gorosei, who even G5 Luffy can do nothing against... and there's 5 of them.
The pirates have G5 Luffy, Shanks, Teach, Kuzan and Mihawk (overrated). The rest of the pirates are fodder compared to an Admiral.
This will be a massacre.