"When he starts killing your people you can use your justice"~ Tek refusing to relnquish his vendetta.
Kahler-Tek is an alien cyborg encountered in season seven Doctor Who.
Kahler-Tek was many volunteers who opted for peacekeeper missions on the war torn Kahler homeworld. Unknown to the volunteers this was a ruse to secure their co-operation and they were subjected to brutal experimentation to create living weapons to end the war.
Tek was among those who did not die on the operating table and became part of the cybernetic army that routed and defeated the enemy in under a week.
After their victory the cyborgs were decomishioned but Tek had been damaged in combat; restoring his original personality and therefore did not shut down when commanded. Horrified and enraged by what was done to him he hunted and killed the scientists who turnned him into a monster. Two however fled the planet before he could exact his revenge.
Kahler-Tek eventually tracked the surviving scientists to Earth and caught up with the first in the American desert. The cornered scientist tried to plead with the cyborg only to shot at point blank range. There was left now "The Doctor" Kahler- Jex.