Lets start listing pre timeskip main villains that have already returned
- Alvida (in cross guild)
- Buggy (cross guild)
- ((Arlong)) through flashback only on fishmen island
- Smoker (Punk Hazard)
- Wapol (Reverie, as king of evil drum kingdom)
- Crocodile ( cross guild)
- Bellamy
- Blackbeard
- Moria (on Fullalead island Perona tries to save him)
- Boa
- the Admirals
In sum 11 main villains returned
Villains that did not return:
- Axe Hand Morgans (his son is still at Kobys side tho)
- Kuro (but his right hand man still was present, while Garp talks about Rocks)
- Don Krieg
- Arlong
- Enel (even-tho he got his crazy moon cover story)
In sum 5 villains did not return ... Did I loose some main villains (I do not count Doflamingo, since he was only a post ts main villain) This means 11/17 = 65% of old characters did return after the timeskip to the story again, which is an ecxeptional result for a long running series imo ....
What are your general thoughts on villains returning into the story after they have been defeated. In my opinion that can get boring, if the character is not seen in a new position / context. So Crocodiles return is more boring compared to Buggys return, since Crocodile is not currently challenged and did not change his personality.
I hope some of the lesser popular characters get their chance to shine at the end, adding "depth" to seemingly unimportant characters.
For example Axe Hand Morgans still does not know he was hypnotized into believing he captured captain Kuro. Because of that hypnosis he became an arrogant high ranking officer. Bringing Axe Hand Morgans and Kuro together could lead to the revelation that his live was built on a lie. And then he could accept his son Helmeppo again, as Helmeppo reaches the same rank as his father through merit. (Currently Helmeppo has the rank below his fathers captain rank)
Personally I think it would be good if Enel did not return. It would be even funnier knowing he is in space living in his own isolated thing without interest in the "real world" and would be befitting of his god complex. This makes the world feel deeper, as there is stuff going on behind the scenes of the main characters, which is good for world building in general.
Villains like Doflamingo on the other hand have huge potential in their relation to the celestial dragons secrets and should return to finish off those plot points.
I agree about Enel, though I do expect oda to tie in some of the space stuff into the AK/VP stuff and there possibly being a reference to Enel, but that's it.
I think Mingo still has a part to play for sure. Oda been low key hyping him up in that jail cell.
As far as who I want to see return, I think maybe Magellan would be cool, though I don't know in what capacity, maybe with the Mingo stuff?
Not to mention the automata that Enel's messing with comes from Karakuri Island - Vegapunk's birthplace.
I'm trying to think how he would come back. Is he gonna be even more godlike? Or will he be sympathetic? What's gonna be his deal? Why come back at all? Maybe to get some piece of tech he's missing for something?
I could just as well see it being left out completely. It's 50 50 for me lol