I'm looking at characters who were changed a lot in a reboot (Jason Todd, Hawkman and Hawkwoman, Donna Troy, Tim Drake, Billy Batson, Cyborg, etc.). Who are some that you think gained/lost the most by being given a new backstory, characterization, power set, or look as part of a larger reboot effort? Not really talking about becoming more or less powerful or even popular, but more or less interesting/enjoyable to you personally.

Now, for my own evaluations, I'm not including the characters that were ceased to exist (even temporarily) with a reboot. Not sure if we should count those who were previously published by others.

I'll start with just a couple characters.

Donna Troy is an easy one, because she went downhill after COIE, but I actually don't think the new backstory was the problem. Not sticking to it was a problem that came later. The NTT in general went downhill, and the others weren't effected by this change. Probably doesn't hurt that I actually didn't like her original backstory anyway, because it did not time out at all with publication history and when Robin debuted and I never liked the retconning of golden age Batman, WW, and Superman as separate individuals from their silver-age versions. So, while I think Donna lost a ton, I don't think the reboot changes were really responsible for that loss.

There's a more split opinion on the Hawks. While Hawkworld wasn't part of COIE, it's kind of bundled-together for me, and so I do count them. A loss for me. I very much preferred the silver-and-bronze-age space cops version. The tricky part is whether you consider their post-COIE selves the same people as their pre-COIE selves and whether that's the same as their golden age selves. If they are the same characters, does the general beginning of the silver age qualify for the "as part of a larger reboot effort"? Anyway, they have plenty of reboot opportunities that fans can think bad or good. So for me, the pure space cops version wins.