The theme of corruption seems to be the antithesis to what the World State is continually attempting to secure; they are trying to keep the status quo by controlling everyone and everything in order to create the "perfect" world and society. Their motto, in fact, is Community, Identity and Stability. So, anyone behaving opposite of that motto is considered "corrupted".  As far as Bernard Marx is concerned, speculation circulates about him because as an Alpha, he is smart, but his physique is not up to par for his class.  Fanny, Lenina's friend, says "It's the alcohol they put in his surrogate" (111), referring to his incubation days and having been corrupted at his creation. Bernard's friend Helmholtz seems to agree with some of the ideas that he has, so he could be considered corrupted, too, because of the alternativeideas that he has from the World State.

From our perspective today, though, everyone in the World State is corrupted because they have all been brain-washed from birth. Their behavior and understanding of life and family is completely different from what we believe today.  Depending on what the assignment is, consider the different perspectives.  If the assignment asks for examples of who is "corrupted" from the World State's point of view, then the answer would be Bernard.