Honkai Impact 3rd: Ex Memorial Arena ver. 6.7 - W4 | Wardens of Tower, Pishacha, DxY | HoHe, VQ, HoT 

There isn't really one "best" since the meta is constantly changing. Just focus on one team if FTP and get the best current units and gear.

In this case, i would say the best characters are the ones that make the best team? That would be full gear herrscher trio. So much coverage and a lot of good scores on many diferent metas

Probably herscher of truth in current meta, she works on many teams

@Thinhago Yeah, Herrscher Trio is probably the best investment you can make right now.

Herrscher Trio. They cover almost all the bosses in the game. And the best character for investment is Herrscher of Truth full set, because she works almost in any elemental teams as support. For physical, grab for Herrscher of Rebirth (impair and crit buff) this coming patch and Prometheus full set (shield break and crit dmg buff) if you have enough crystals. NOTE: Meta is changing, but these valks that I mentioned are the ones in meta right now and covers almost all the bosses. I just started playing last February (Version Kiana), and I can constantly stay in Agony III - Redlotus right now, SSS MA, and Abstinence/Finality Elysian Realm.