Papo y Yo is pretty good, but it’s a struggle to describe it as being about plurality in any way

Kiln People’s pretty forgettable, and the only character who could be described as plural has a secret evil alter.

Parasyte is one of the few examples of body horror that actually works on me. Pretty good if you know what you’re getting into. I guess it fits under your definition of plural, and Migi isn’t evil per se, just a very pragmatic sociopath.