Doctor Who: Every Version Of The Doctor Explained
11. The Metacrisis Doctor (First Appearance: 2008)
The Metacrisis Doctor was a genetic hybrid built from the combined DNA of Donna Noble, and the Tenth Doctor's severed, pickled hand, which he had lost in a sword fight in the 2005 Christmas special.
This half-human/half-Time Lord clone of the Tenth Doctor eventually triggered a catastrophic explosion that practically destroyed the new Dalek Empire.
The Tenth Doctor was furious with his counterpart, which was a bit rich considering the whole Racnoss-drowning incident, and exiled the Metacrisis Doctor to live in a parallel Earth with Rose Tyler, believing that she could make him a better man.