If this is a bug, it is the good kind. I just got the top level Shadow Vigilante challenge completed in the game, even though it seems I shouldn't have. The requirements say you need to reach 50x combo and 15 variations in a fight, among other things. But for some reason I just got that in a fight where the stats read 42 combo and 10 variations. Does anyone have any insight into this?

I've read the bug is that you can meet each condition separately in different fights. Perhaps you had reached 50x combo and 15 variations in one or two other fights, and then won a fight without any damage?

At any rate, yeah, this seems to be easier than the text suggests (which reads like you have to do all three in one fight)

This happened to me not too long ago. If it's a bug, I sure as shit ain't complaining.