In many science fiction or fantasy books, the heroes often face the so-called “lesser evil principle.” For example, when a good guy does something bad—but it is justified by the plot—because otherwise, good cannot win. In particular, if you remember the Harry Potter books, the protagonist performed a bunch of unforgivable curses—but was never actually punished for it…
Okay, we are not talking about that now, although the lesser evil principle is also relevant for this very real story from user Huhy, whose sister, sick and tired of living with a flatmate who was a slob, ended up literally stealing her part of the rental deposit. However, let’s not get ahead of ourselves.
More info: Mumsnet