That said everyone knows Niki/Ayane/Maya are at the top of the list, what about characters you didn't expect to like?
Funnily enough my answer to this question is the same.
Niki started off as a stereotype bitchy ex, was super boring and I didn't like her pop star aesthetic at all. Fake and entitled. So seeing her turn out to be so sweet and caring completely flipped this on it's head. Even at first I felt it was mildly redeeming but not too much, but seeing how she's taken so much initiative for Akira and Ami really pulls at my heart strings.
For a less boring answer I'd go Kirin or Otoha, maybe Maya too.
Kirin is, frankly, still kinda shitty but at least is learning a bit. What she did to Ayane was downright nasty of her and watching Ayane borderline choke her over genuinely felt good. Ruined a friendship for nothing. That being said it seems she's started growing a heart recently, I hope it stays that way.
Otoha did Rin dirty and she can die. But her recent events haven't been awful, there's some good there and I appreciate that she doesn't beat around the bush with Sensei and admits (most) of her faults.
Maya was just
too tsundere and it was annoying, saw her plot twist coming a mile away (that she liked him, not the other one) but the way it was executed was great.
Huge fan of how Maya Prime ended up and I want her to come back so bad.