I know of some remarkable curse tablets of slaves that condemn others (e.g. an opponent in the chariot races), but I was wondering whether they also wrote them to 'hurt' their social superiors (be it their owners or a free man/woman in general).
As far as I know, we don't have any specific examples of what you're looking for. That's not to say it didn't happen, just that we haven't found a surviving example. This website has some really great examples of defixiones found in Britain. You'll notice they're mostly condemning thefts, a common problem around baths.
We do know some slaves would obtain lead tablets with magical inscriptions that were supposed to allow them to escape without being caught by their master, but those weren't defixiones.