I'm still scratching my head over Byakuya helping Muramasa; it just feels so against everything we know about his unwavering loyalty and honor, making me wonder if there's a bigger play I'm missing. His clash with Kenpachi was still incredibly satisfying though, even with all the divisions crumbling, but man, Mayuri blowing up his own Zanpakuto just to poison everyone is truly the most twisted and effective move I've seen him pull, securing his spot as the scariest captain.