Katerina Ivanovna Marmeladov
Katerina lives in the past. But, hey, we would, too, if we were married to Marmeladov.
As far as we can tell, she was born in a fairly prosperous and "respectable" family, with a degree of privilege. She just didn't have good taste in men. When we meet her, she's both mentally and physically ill, with no hope of treatment. She's also extremely abusive. She bullies Sonia into prostitution and beats her children. She says terrible things about foreigners and is confrontational and violent with people she doesn't like—she's the Russian novel equivalent of the worst type of YouTube commenter.
Still, Raskolnikov has compassion for her and doesn't seem to judge her. Perhaps because she's poor, he doesn't place her in the same category as he does Alyona the pawnbroker or others he considers victimizers. As with Marmeladov, our own compassion for her is strengthened by Raskolnikov's.
Incidentally, Dostoevsky and his mother both died of an illness similar to what Katerina suffers from—lung problems, possibly tuberculosis, which was not uncommon in the 1860s. Take a moment to be thankful you live in the 21st century, everybody.