The Master

A particulary incompetent version of the Master attempted to destroy the Doctor on the planet Tersurus.

Biography
While spying on the Doctor, the Master inadvertently enabled two way communication, and unwittingly revealed several of his plans to eliminate the Doctor. After the two had arranged to meet on Tersurus, it became apparent that the Master had travelled back in time to bribe a Tersuran architect to install several traps in the castle they were now in. Unbeknownst to him, the Doctor had also done the same, bribing the same architect to change the details of the traps. This eventually led to the Master floundering around in the sewers of Tersurus for centuries, after which he was forced to ally himself with the Daleks, as they were the only life-forms without noses, and hence the only creatures willing to work with him.

As part of this alliance, the Master had himself "augmented" with Dalek technology, resulting in not only a more youthful appearance, but also "Dalek bumps" installed on his chest. Although he remained adamant they were etheric beam locators, the Doctor continually teased the Master because they resembled breasts.

When he believed the Doctor to be dead, the Master renounced his evil ways, before the Doctor regenerated into a female form. Attracted to each other, the Time Lords walked off, arm in arm. (DW: The Curse of Fatal Death)

Behind the scenes

 * Like The Curse of Fatal Death, this version of the Master is not considered canon.
 * He has been called "The 17th Master" by some fans, based upon a behind-the-scenes featurette on the making of the spoof. In the special itself he is not referred to as anything but the Master.