So we know Big mom is stupid powerful but just to give a hint. Marco would probably brutalize Luffy and and admiral would do the same to Marco....and a Yonkou would probably (and has) fucked up an admiral. Though it's not surprising Luffy always jumps into battles with people stronger than him only to grow immensely before fighting that person. We might finally get some sea battles! This is promising to be the most epic showdown since Luffy beat Crocodile.