This is what I'm finding about 50 hours in, nearing the end, Hard mode GD.
Lysithea is a monster, as has been stated numerous times in this thread.
Claude hasn't had a problem one-shotting almost anything since level 1, and one he got his advanced class, goodness. And Hilda...
Idk if my Hilda (Fighter->Brigand->W. Rider->W. Lord) got lucky with growths or something but she's an absolutely insane shock trooper from go. She one-turns anything I've faced, and Canto lets her fly away immediately. She had some hit problems early/mid, but these were easily resolved with Smash. If I wanted to, I could Warp her in anywhere to two-turn any commander I've faced so far. My eyes pop a little bit when I see people rate her low