Bolog

Bolog was a villain who once concealed the whole Reptilios Invasion Fleet on the dark side of the Moon in their effort to conquer the Earth. However, the Doctor, helped by Romana and K9, sent the Fleet into orbit with a banana.

Some time later, Bolog joined forces with other aliens to try to kill the Doctor, their common enemy. He shot Questor in the face, believing him the Doctor in disguise.

Later, caught in three-way shoot-out, he was shot by the alien known as "Plink" and simultaneously killed the Mentor. (DW: Death to the Doctor!)