As more of a classic Legion fan, I've always found some of the Reboot characters hard to get a grip on, but Candi has, at least in the books I've read, had the most compelling and fun characterization. Particularly on a team so full of people having drama, she was a breath of fresh air, just sort of cheering up the room with her sunny disposition and welcoming nature (which made me, as a reader, feel welcomed!).
I was annoyed at her death, to not even advance another characters story, but to instead destroy that character! (Kind of the opposite of fridging, in that the lady doesn't die to advance the dude's story, but to instead tear him down and show how unredeemably bad he was now).
On the other hand, regarding Candi's upbeat and pleasant personality being a breath of fresh air, Gates' curmudgeonry was also fun, if the exact opposite and not at all a breath of fresh air!

As much as I love Kid Quantum 2, I feel like she didn't get nearly as much personality or development as Candi or Gates (or Shikari or Kinetix or XS, who also seemed to get a bit of focus, as opposed to characters like GEAR and Thunder, who did not, that I saw).