In terms of individual characters the one who has benefited the most from the Krakoa era is Cypher. He has never, ever been this relevant or important. He hasn't actually appeared much, but his status as a mover and shaker is astounding considering his history and how little he was used even after he was brought back. His marriage is still ma take it or leave it thing since it came out of nowhere and they haven't done anything with it, but that's a minor thing.
Xavier is back on top for the first time in decades. While he's made a lot of questionable moves, both morally and in terms of intelligence, there are people who are adults now who were born after the last time he was the leader of mutantkind and not an irrelevant afterthought.
Gabby has gained many new fans thanks to her earnest and sweet characterization in this era. Who would have thought that the only compelling Wolverine-type character in this era would be a clone of a clone?
The entire cast of Hellions. Nanny, Orphan Maker Greycrow, Kwannon are all much more beloved now than they were 3 years ago. Sinister's stock has gone up as well.
Emma had been regressed to a villain again in the years prior to HOXPOX and that's all pretty much forgotten now, with her now being depicted as one of the most moral members of the Quiet Council while still getting to scheme for more power.
Mystique/Destiny: Destiny being back is a big deal in and of itself, and both are more relevant and powerful than they've been in a long time.
Long-dead characters who were brought back like Synch and Thunderbird.
Cyclops is fully out of his 'do whatever is needed to survive' phase and is back to being a full-time boy scout.
Magik's superstar status has been cemented even though she hasn't gotten much on-panel development like some of the others.
Apocalypse has more depth now, though your milage may vary on whether that's a good thing and it meant he has been written out of the books for now.
In terms of characters who've suffered, there's Colossus, who 's been reduced to a pawn of others with no agency whatsoever.
There's everyone who's been written by Tini Howard except for Apocalypse. Most characters were wallpaper, Rictor had his odd relationship with Apocalypse that no one likes, and Betsy became unlikeable in what amounted to her stealth solo.
Rahne has been a whiner and became partially responsible for Gabby's murder, so this has done nothing for her.
Bishop has had no use that justifies making him a captain or the captain commander.
Rockslide got killed off for shock value and nothing has been done with his resurrection gone wrong. Most of the New X-Men class remains stuck in their trainee stage.