200Def/252SAt/56SpD
will always survive a non-crit Cruch from a max attack Ttar or Dark pulse from a max Special Attack Hydreigon (not counting life orb, will sometimes survive Crunch, and never Dark Pulse, but no one runs max SAT hydreigon do they?)
Reuniclus with life orb can always OHKO Blissey with Psyshock and OHKO Eviolite Chansey every 5th time (~20%) Choice specs obviously would be OHKO on almost anything that doesn't resist the hit.
Zoroarks should be avoided and other fast darks such as weavile