So, there are a whole bunch of powerful characters in one piece, but it's kinda hard to gauge their strength though.
Would you guys say Garp is as powerful as the Admirals? At first it seems like he's not, at least to me anyway, though we haven't seen him fight very much (I'm an anime only person). But if you look at other facts, he does seem more formidable. He's definitely stronger than any of the other vice-captains and apparently he refused promotions (meaning he was probably offered position of admiral). In the past, he was one of the major power figures of the world up there with Sengoku, Gol D. Roger, and Whitebeard, the latter two are stronger than Admirals (at least in my opinion I would say Whitebeard is stronger than an admiral and Gol D. Roger was probably a tiny bit stronger than him). Compared to Sengoku, considering that they have worked together for so long, I'd say he's only a little weaker than Sengoku. How would you guys measure Garp's strength compared to other characters?
And then we have Sengoku, sure he's the fleet admiral, but rank I don't think necessarily means he's the strongest in the navy. Both him and Garp are old men and they are probably past their prime. Would you guys say Sengoku is stronger than the admirals? Though I am an anime only person, I do read the one piece wikia quite a bit and found many many spoilers.
Then we have the schichibukai. Generally, I think they are all weaker than the admirals, but I could be wrong. Do you guys think any of the Schichibukai can stand against an admiral? Who do you guys think is the strongest Schichibukai? Mihawk is probably up there, but Doflamingo is one of those enemies that seem to be very hard to kill. Kuma may be up there as well considering that all the fights I've seen him participate in so far have shown him winning fairly easily. Blackbeard will probably end up being one of the main antagonists in the end.
Crocodile I want to single out separately. From all of the spoilers that I've read on the one piece wiki, it seems he fights on par with all of the other schichibukai and enemies, but these same characters seem to also be a great challenge to Luffy, even though Luffy defeated crocodile when he was much weaker than he is now, they are fighting the same enemies with about the same amount of difficulty. I doubt that he's any stronger than he was back then, how would you guys explain this?
Another group of people are the Whitebeard commanders. It seems the lower the division number is, the stronger the commander.
! Marco and Jozu were able to fight pretty well against admirals. However, I do find it hard to believe that Ace would be able to do well against an Admiral, even though his division number is higher than Jozu. Perhaps I'm wrong about the division number = strength concept. But once you get higher into the numbers, they seem to be about as strong as vice admirals.