I finished my "new game plus" in the GBA remake, wanted to recruit everyone and collect all cards this time. Musashi is quite strong, but Max is just the best unit by far, and unlike in my first playthrough I didn't even use any of the stat-boosting items (the turbo pepper is the most tempting). Max seems to know he is awesome - after promoting he often just sort of "bitch slaps" the air, sending a shockwave that kills the enemy (I've gotten this alternate animation both when he gets a "Super attack" but also without getting the critical).
With the White Ring, Black Ring and the Chaosbreaker equipped (and mostly he is the only unit that can equip those) he can cast Aura lv 2, Blaze lv 2 (mostly useless faced with Chaosbreaker spell) until the items decide to show cracks (you can then repair them) and Frost level 4 (I think you can just do this all the time as you can't crack the Chaosbreaker). Then he still gets enough MP to cast 2 or 3 Supernovas, and he can simply attack with a high natural stat and the powerful Chaosbreaker.
Mawlock can do a lot of imbalanced stuff with the cards, but the most broken thing is very likely using Max's card and Mawlock's card (with perhaps 2 other ally cards) to give Max (with perhaps 2 friends) 3 moves each turn. I never actually tried that but must be quite fun - by turn 3 you get your 3 best units end up moving twice, then re-load the cards with Mawlock's card, turn 4 Max moves three times and by turn 6 you get 18 moves (12 regular+the extra 6) each turn!
racketboy and racketgirl are in chapter six--we have had a lot of fun playing! I had never heard of it before and I really got into it racketboy often ends up watching me play!