Basically what the title says. There’s always discussions about someone being force sensitive and how they could use the force or not sensitive to it at all, but has anyone ever been completely immune to it? Like if Vader was doing a force choke and the person was just like “why are you holding your hand up like that? What are you trying to do?”
Sounds like you’re thinking of the ysalamiri.
Additionally, also only in Legends canon, there are also the Yuuzhan Vong, a species from outside the Galaxy that was entirely unconnected to the Force. They could not be sensed through the Force and were immune to most Force abilities that directly targeted them, though they could be affected by some abilities, i.e. telekinetically thrown objects or Force Lightning.
I’d like to see someone be immune to telekentically manipulated objects…. Rock bounces off someone “sorry, you used the force to do that”.
“I’m a ghost!”