This is a theory on why Sanji never gets any good limit breaking fights and why this seems to be very significant for the story.
People seem to always complain about why Sanji hasn’t had a proper 1 vs 1 ever since the start of New World but this isn’t actually the problem of New World only.
Sanji has had barely 2-3 proper 1 vs 1 fight ever since he joined StrawHats.
Ever since his introduction, he always either gets cheap shotted or blackmailed into not fighting. Here are some examples:
Sanji vs Gin (sanji was blackmailed and attacked off guard)Sanji vs Kuroobi (he kept taking Sanji under water because he could not hurt Sanji on land)
Sanji vs Bon Clay ( Bon Clay kept changing to Nami so that Sanji won’t hit him)
Sanji vs Absalom (he took Nami hostage and gave Sanji a crap ton of injuries without Sanji defending himself at the risk of injuring Nami).These are just some examples I could think of off the top of my head and I’m sure there are more.
Now there are two reasons why Oda doesn’t give Sanji good fights. Either he isn’t sure how to handle the character or there is a reason for it. If it was any other author, I would blame bad writing but Oda is smart and has planned something for Sanji.
So why lack of close fights and limit breaking fights important for Sanji?
Because I believe close fights are the key to unlocking Sanji’s full power and potential.
As mentioned by Vinsmokes, Sanji and his brothers have had their genes modified and have a dormant hidden power within them. All sibling managed to unlock their power and have had success in using them except Sanji (even though the modification was successful). Now if you remember a while ago we had flashbacks of Vinsmokes training and doing things like swimming and other activities that require lots of stamina and require you to push yourself. This piece of information is important as it means that physical activity is required to activate this gene. While this is the case normally I believe the training Sanji went through as a kid may have been too easy or more likely not physically straining in the “right way” and as such, he haven’t had any reason to unlock his power. Now during his training at Okama island, he may have been pushed to his limit but wasn’t quite pushed far enough to unlock his power. Sanji’s training may have been actually perfect for him as he wasn’t really taught how to fight but rather had the opportunity to battle day and night which means he was strained in the “right way”. Why wasn’t he pushed hard enough you ask? It’s because the Okama weren’t trying to kill him and we’re actually trying to get him to join them.
So you may ask what does this mean for the character? It means that Sanji is on the verge of awakening his power and is probably 1-2 close battles away from unlocking it.
Now I believe during the end of current arc (Big Mom arc), Sanji will have a final battle with Judge or Ichiji and will end up beating either one of them resulting in him getting a glimpse of his true power. This doesn’t mean he will fully unlock it, he will probably just get a feeling of it and this will cause him to train in the right direction.
All StrawHats will eventually need a huge power up and at this point in the story, it would be too early for Sanji to get his full power.
Luffy will get his devil fruit awakening.
Zoro will probably gain an advance version of haki or will unlock the full power of ashura.
Sanji will get his full potential.
*Theory by Levosire