^No matter who ultimately faces Luffy, they will always be "used to put him over" because he IS the series' central protagonist. However, this is not a detraction from how powerful, cunning or otherwise ruthless Luffy's opponents are. We've all seen Oda isn't above Luffy losing to those who are in fact more powerful than he; he lost to Crocodile twice before finally adapting to the situation and defeating who is quite possibly his greatest natural enemy (sand vs rubber) outside Akainu or Aokoji (heat/ice vs rubber) (who both defeated him once themselves); Eneru actually "crippled" Luffy before Luffy, unaware of his natural conduction, annialated his foe, who had Luffy as his greatest natural enemy; Magellan nearly eroded Luffy following their first encounter, and it was with innovation and wax support that the latter finally defeated his foe. No matter what experience Luffy faces, he is going to have set backs which ultimately further his fighting capabilities and place him "over the top." That's story telling and regardless of character preference, Luffy will always overcome his challenges. Hahaha just wait until the SHs have to face Shanks and crew, everybody is going to go berserk with rage that Luffy transcends his mentor!!!