I have way too many bands that I absolutely love that broke up too soon...
The bands from the early 2000's Level Plane roster; City Of Caterpillar, Majority Rule, Pg99, Malady, Orchid, and probably a few more. The thing is, that scene was so damned incestuous that all of those bands shared members multiple times. It's a maddening display of great music that burned fast, but burned out almost immediately.
I think Fugazi broke up 'went on hiatus' at just the right time, but I wish I had known about them when I still ahd a chance to see them play.
I wish Modern Life Is War had not broken up last year. I wish Steve Sindoni was still doing vocals for Breather Resist, but the rest of them went on to form Young Widows, so that's okay.
I wish my band hadn't broken up without at least playing a final show.
Fuck...now I'm music-depressed.