#39 Toberman
Toberman was designed to be deaf and to use a hearing aid. There was supposed to be a scene with Roy Stewart wearing a hearing aid and interacting with the other characters through sign language, but those details were lost in translation. What fans got instead was a black man who was illiterate and, therefore, treated as a primitive being and a slave.
The explanation “He was meant to be deaf” is not very helpful when introducing people to Tomb of the Cybermen for the first time.