Idk about you guys but the characters that give me the most problems are probably Yosuke, Yu, Minazuki, Sho, Yukari, and Yukiko
Having faced enough Naotos to really say how I fare.
Also I kind of wish 5B on whiff didn't go into the subsequent hits or if it required 5BB instead. Gotten punished badly on a lot of dropped AA 2B combos :[