Crystal Peony

The true / best-ending achievement: in a single run, earn the top "A" or "EX" epilogue for every named character. That means recruiting all leaders (including secret Matilda and Red), completing every character's weapon side-quest for their EX ending, never killing a named enemy Leader, and saving all named NPC allies. Difficulty and item-% don't matter, and it's doable in New Game+.