Terminal velocity is entirely a product of air resistance (or in general, resistance from any fluid medium). That's mostly caused by electromagnetic interactions (AFAIK) which despite physicists' best efforts is still best explained as a "real" force. Hence why objects with different shapes or masses can have very different terminal velocities on Earth (and the same is true if you vary the atmospheric composition, or consider objects falling in water). But they will all fall at the same rate in a vacuum, unless the object is massive enough for gravity to warp the trajectory of the object onto which it's falling.