Probability Manipulation (bad) – The ability to make unlikely bad events more likely.
Black Cat (Marvel) is a cat burglar causes bad luck but the power is subliminal.
The Scarlet Witch (Marvel) who can make bad unlikely events more likely i.e. she can hex someone.
Domino (Marvel) has both good luck and bad luck generation! In combat, she has good luck and her opponents have bad luck!
From Brigade Sourcebook #1, Crucible can cause bad luck in the Wildstorm universe.
The Chaos Globe can emit a field of random magical instability in Creature Collection II. Dark Menagerie.
The Wizard (Marvel) creates a pocket of none casualty that is more or less a hex in Avengers Spotlight V1 #26.