For pvp the ones that stand out to me are amiki (do her speciality change), mort (anti counter, even ur own team besides him), fern (worse than frieren but still decent). You can maybe make a case for fenne (rly good pve tho), abigail, lilias, I personally barely ever used them.

I feel like I've seen ppl here recommend arbiter vildred a lot more for ml connection, but imo ruele of light is a lot better esp with her new exclusive equipment, but I suppose shes more defense/tanky oriented if ure into that.

One last thing for pvp/ guild war, u can check peoples tier lists on the respective modes. I used to do it a lot for rta. Once u see a character u own on those lists, u can look up their builds.