The Fifth Doctor Who

The Sixth Doctor (played by Colin Baker) began life after the fifth incarnation died after a lethal exposure to spectrox, contracting the lethal spectrox disease. This regeneration left the doctor in an unstable mind, with bouts of near insanity and violence at one point even attempting to throttle his companion Peri to death.

The Doctor decided to exile himself on Titan III but soon became embroiled with stopping Mestor and his Gastropods. After some time the Doctors personality settled down and he developed an extremely large ego, deciding to fix everything that was wrong with his TARDIS.

Eventually the Doctor began to travel again with Peri and it was during an adventure with Peri on the planet Thorus Beta that the Doctor was captured by the Time Lords and once again put on trial.

In capturing the Doctor, he was taken out of time and as a consequence had partial amnesia. He was accused again of interfering in the affairs of the universe, being prosecuted by the Valeyard. The Valeyard falsified some evidence during the trial and eventually it became apparent that the real reason for the trial was to cover up a conspiracy of a corrupt council of Time Lords that the doctor had unknowingly uncovered.

The populace of Gallifrey became aware of this and threatened to overthrow their leaders, in the end appointing Darkel as Lord President.

This Doctor's personality was quite unpredictable, arrogant, self absorbed, stubborn, tasteless, childish and argumentative. This was a Doctor who did not suffer fools gladly; he sometimes seemed to endure his Companion's presence far more than he actually appreciated it, and held himself as superior to almost anyone he encountered.

The Sixth Doctors time came to an end when the TARDIS was attacked by the Rani, forcing a regeneration into the seventh Doctor.