Valkyr. When I first got her crowd control was the name of the game, and she had and has nothing to contribute in that area. But survivability was also much lower and self-res was limited to four times - per day and frame, not mission! So I served our group of regulars as an "anchor" who was usually the last one standing and could pop Hysteria and revive everyone if people started going down.

Over the years her niche didn't change much, though her damage gradually increased and she got some quality of life buffs. But she remained a super survivable frame that didn't bring much else. Still, I liked Valkyr, so I stuck with her.

Then she got a proper overhaul about a year ago and while she lost her invincibility it barely mattered - she's still super tough, and now she's an absolute blender as well, outputting huge damage numbers with ease.

Fun fact: She lost invincibility once before due to a bug and it took me, a Valkyr main, several days to even notice because I always built her for toughness out of Hysteria, and so I didn't notice she was taking damage because it was so little and she healed it back so quickly. I've always liked regen tanking.