Thought of another that might qualify.
The Spell of the Black Dagger
is possibly the darkest work in Lawrence Watt-Evans' high fantasy normally light-to-comedic Ethshar series.
The antagonist is one of the viewpoint characters, and you can see her slide into justifying her self-serving actions which gradually escalate in ways I won't spoiler you for. While she doesn't exactly get away with it, the people up against her don't exactly come out unscathed, and in fact there may be more problems for some of them than get solved.
This is available as DRM-free MultiFormat via Fictionwise
(so you can use the weekend discount coupons), and Watt-Evans has put up a number of his Ethshar short stories for free reading online (I recommend Sirinita's Dragon
as being closest in tone to SOTBD, if you're interested).
You can read the novels mostly standalone, although some have main characters who show up as guests later (SOTBD has some characters who were in With A Single Spell
play a medium-important supporting part).