Sadism usually enjoys inflicting the pain, whereas I understand schadenfreude as just enjoying it whether or not you were involved in causing it. Most times I've seen it used the person enjoying was not part of the cause.

An example would be maybe the Herman Cain awards subreddit. Anyone there was most likely doing the opposite of causing the problem, but were enjoying when people who did cause issues got comeuppance.

(For anyone not sure what that subreddit was, it was specifically showing when people who denied covid got sick and or died themselves. It wasn't for anyone who had Covid, just for people who they could also show vehemently and dangerously denied Covid and/or showed how they harassed others about it).