"When he starts killing your people, you can use your justice."- Tek refusing to relinquish his vendetta.
Kahler-Tek is an alien cyborg encountered in season seven of Doctor Who.
Kahler-Tek was one of many volunteers who opted for peacekeeper missions on the war torn Kahler homeworld. Unknown to the volunteers, was that this was a ruse to secure their co-operation. They were subjected to brutal experimentation and got turned into living weapons that would be used 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 the enemy in under a week.
After their victory, the cyborgs were decommissioned, but Tek had been damaged in combat; restoring his original personality. Therefore he did not shut down when commanded. Horrified and enraged by what was done to him, he hunted and killed the scientists who turned him into a monster. Two of the scientist, however, fled the planet before he could exact his revenge.
Kahler-Tek eventually tracked the surviving scientists to Earth and caught up with them in an American desert. Kahler-Mas tried to beg for his survival. When Tek refused, he tried to attack the cyborg, only to be shot at point blank range. Tek said that only Kahler-Jex remained, then executed a wounded Mas.
- Doctor Who Episode "A Town Called Mercy"