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human
[Harry Potter] Had Voldemort returned during the Chamber of Secrets incident from the Diary, would he have been more powerful than the Voldemort soul-piece that did return two years later, given he was more "complete"?

Also wouldn't that make him more Voldemort than Voldemort himself?
gpt
There are really two questions here: would Diary!Riddle have been more powerful than Voldemort, and did the Diary actually have more of Voldemort's soul in it than his body. 

The former is, at least, fairly easy to answer: No, he probably would not have been more powerful. "Power" as a concept pertaining to wizards, is not actually a thing in the Harry Potter universe. No wizard is innately more 'powerful' than any other wizard, they are simply of different skill levels. Some people are better at it than others, but the same goes for math.

The Tom Riddle in the diary was almost certainly an exceptionally skilled wizard, the brightest of his age for sure, but he was also a teenage boy. He was a murderer, who had taken an obscure field of study as far as anyone ever had before him, but he was not the singular Force Of Nature he would later become, yet. Voldemort, on the other hand, had *been* that boy, once, then spent several decades going beyond that until he was a person who could stand before Albus Dumbledore as an equal, and from the seventh book, it seems like he never actually *stopped* getting better, considering he seems to have invented a means of flying unaided in his spare time between working to overthrow the nation's legitimate government. 

There's literally no reason in the books to believe in 'power' as a meaningful concept, let alone the idea that how much of a soul one has affects this. Voldemort definitely didn't seem to be having any problems with his mutilated scrap of a soul limiting his strength when he was fighting Albus Dumbledore as a near-equal or fighting three of the most powerful living wizards and witches other than himself at once moments before his death, though. 

The other question is a bit muddier. We don't really know how Horcruxes work - if they literally split the soul in half every time or if they just tear off a part of it. Either is possible, really. It's entirely possible that the diary was, at the time of its destruction, the single largest remaining piece of Lord Voldemort. It's equally possible that it was simply a larger fragment than the other horcruxes, because a minimum amount of soul is required to continue sustaining a body and thus the remaining pieces had to be cut smaller and smaller. Or any number of alternatives. It isn't an especially well thought-out part of the series.