What's one plotline in Bleach that you feel was somewhat abandoned and you wish had been explored further?

For me, it's Mayuri and his questionable experiments. I know the Gotei weren't exactly saints, but Mayuri really pushed the limits with his inhumane practices. We all know about his experiments on Quincies, but there's no guarantee he didn't do the same to Shinigami as well.

Then there's his history with Uryu. I can't stand how they completely dropped this plotline and reduced Mayuri to just another morally gray character. Through him, we could have delved deeper into the world of Bleach and possibly gotten much richer world-building.

Another missed opportunity is the lack of exploration of Komamura and his clan, which was never touched upon at all.