Well it can depend on the battle, however, I find Cynthia to be a little too hard to kill which makes her a strong pick for the strongest. Her life draining attacks often times full heal her and she's very hard to take down quickly which means you have plenty of survivibilty to just use her life drain abilites whenever she gets low. I think the game is balanced enough where shes not too broken tho as she can deal good damage but is not putting out as much as an optimized ligaea or Ariadne spreading burn damge. Ironically I found Lorena to be more of a letdown but I probably am not optimizing/using her right. It feels like shes a good jack of all trades but if i want magic damage you go aria, tanking go cynthia, physical go ligaea, and healing go Calysia, and if you want to take a nap go Somnus. Her freeze is nice tho but Somnus might be better at CC with his sleep. Like I said tho I think the game is bery balanced and doesn't have especially broken or weak characters.