~ Goku Black getting stronger from the pain dealt to him by Goku
Sadomasochists thrive off of pain, whether it be the pain of others or pain inflicted on themselves. This is most common in villains who are sex fiends, Perverts who endanger others for the thrill, self-loathing/Suicidal Villains who use pain as a coping mechanism, or maybe two or more villains who feed off each others' pain and keep the circumstances going out of mutual need.
Please note that Sadomasochists differ from Sadists, who only get pleasure from pain inflicted on other people. Sadomasochists don't just enjoy pain; they get a fix out of it and need it as opposed to wanting it. They also differ from Masochists, who only get pleasure from receiving pain, but don't strive to find it; they merely enjoy it when it comes to them.