It's really quite simple, tactics - just beat bandits strong attack, then gain stamina, and so until you kill. Nomu, you have to protect himself with "Quirk protection", then hit him with a strong attack, and after a couple of hits use "Speed Storm". That's about how it can be defeated, but you can experiment in different ways. However, you may have encountered a bug, which damage accumulates, it occurs because of the checkpoint, to bypass it, you need after losing do not continue to play with checkpoint, and boot to save made before the fight.