Feverpitchfiasco and I were talking about Jack Harkness and his capacity for darkness. I’d mentioned how utterly terrifying he could be if ever truly stopped caring. A smart, inventive, clever human with thousands of years of experience who simply cannot permanently die no matter what you do to him. Even a Timelord Victorious might eventually run out of regenerations. Maybe that’s why the Doctor disabled his vortex manipulator, or part of it, he could see the potential there. And we already know Jack has a dark side.

Thankfully, Jack tries to do good in the universe, but there is that potential for very terrible evil.