One of the best short stories ever written about this type of internal corruption is "The Edge" by Agatha Christie. It isn't one of her mystery stories; rather, it is usually found in her ghost/occult short story anthologies and is incredibly creepy.
I will now give away the plot.
In the story, a upright, virtuous, charitable, socially respected, attractive woman, Clare, becomes downright evil.
The corruption begins when she discovers that Vivien, the wife of the man who jilted Clare, is having an affair. Clare decides not to tell him, praising herself for such disinterested goodness (it would only hurt his feelings; she would be telling him for the wrong reasons . . .). Actually, her true motive (or, at least, one of her initial motives) is a sense of power. When Vivien behaves in a catty fashion, Clare lets her know what she knows. She makes Vivien promise to give up the affair for Clare's silence.
Clare is only partly silent, however. She uses subtle, cutting remarks in social settings to remind Vivien what she knows. This goes on for years until Vivien finally persuades the husband to move away. When Clare finds out, she virtuously informs Vivien she can no longer keep silence.
"I daresay it seems very strange to you," said Clare quietly. "But [my reason] honestly is [conscience]."Despite Vivien's correct surmise, Clare holds to her intent at which point Vivien throws herself off a cliff (it sounds far more dramatic and surprising than written; in the story, Vivien's decision has a dream-like quality: she runs off waving as Clare watches stupefied). Clare goes mad.
Vivien's white, set face stared into hers. "I really believe you mean it, too. You actually think that's the reason."
"It is the reason."
"No, it isn't. If so, you'd have done it before. Why didn't you? I'll tell you. You got more pleasure out of holding it over me--that's why."
Setting aside the initial issue--which isn't really the point--Clare's relishing of power over a single human being in a small village in England is exactly the kind of mundane, petty cruelty that can occur at the purely interpersonal level. It is remarkable storytelling--and proves that while Christie may not have gone in for long exploratory novels regarding human behavior, she certainly understood it very well.