Super Strong Item

Parasite Scarf It becomes an AoE attack permanently and almost always crits, so if you give it to a single-target attacker, you can one-shot enemies (I gave it to my 'Indifferent' character). If you give it to a healer, it becomes an AoE heal and can also clear debuffs. A similar item would be the Jellyfish Scarf. I really should level up my items properly, but since there's no reset, I can't really experiment with things.