I haven't seen M15 (in fact, has it ever been shown in the UK yet?!), but from what I've read, Kyurem is another unfortunate patient of misunderstooditus, being just eager to finish a fight Keldeo started. Granted, since he's in an antagonistic role (and since that may as well be a fight to the bloody death), he doesn't seem to suffer the Darkrai-type.
Plus, Kyurem does seem to be pretty scary, seeing how the thing's practically unstoppable. To quote Cracked: Keldeo vs. Kyurem "is sort of like showing up for a knife fight with the Death Star." Kyurem's the Death Star, in case it wasn't clear.
Also, how bout those Genesect? Seem pretty evil to me so far.