Gavrok

Gavrok was the ruthless and merciless leader of the Bannermen. Assigned to wipe out the Chimeron species, Gavrok and his group followed the last Chimeron queen, Delta to Earth in 1959.

During the incursion to Earth, Gavrok killed a group of Navarinos who were simply on a tour, and later booby trapped the Doctor's TARDIS with a Sonic cone. Ultimately, however, the singing of Delta's daughter caused Gavrok to stumble into the Sonic cone's defence perimeter, and he was atomised. (DW: Delta and the Bannermen)