Master

Renegade Time Lord, power-hungry "lover of chaos"
Once friends with the Doctor, eventually became enemies
Pit himself against the Third Doctor & UNIT during the Doctor's exile on Earth
Fled the Time War, turned himself into a human baby using a Chameleon Arch;
Personality was reawakened by Martha Jones, regenerated into a younger body
Election as Prime Minister of the United Kingdom in the 2008 elections;
Sought to use the Earth to create a new Gallifrey, defeated by Martha & the Doctor
Stabbed by a future incarnation of himself, to ensure his regeneration into her;
Attempted to redeem herself & fix their friendship with the Doctor
Shot by her past incarnation, causing her to regenerate
Returned to Gallifrey, destroying the entire civilization
challenged the Toymaker to a game, lost & was imprisoned in gold tooth