Androvax

Androvax was an enemy of Sarah Jane Smith.

History
Androvax was the highest on the Judoon's most wanted list, being wanted in five galaxies for 12 counts of global destruction.

He was eventually caught by Captain Tybo, but during transport the ship crashed, allowing Androvax to escape. He knocked out Tybo and escaped, taking over the body of a young girl. However, when Sarah Jane Smith detected him he revealed himself, stunned Clyde and entered her body instead. He then returned to her home in Sarah's body and instructed Mr Smith to self destruct, before proceeding to the Genetec Systems and instructing the microscopic nanoforms to build him a ship.

Androvax was finally caught when Luke threatened to sabotage the ship, and ultimately stopped the Nanoforms from destroying the planet. The Veil was then sentenced to execution.

His reason for destroying planets was jealousy, as his planet was lost. Rather like the Doctor, he was supposedly the last of his kind. (SJA: Prisoner of the Judoon)

Behind the scenes
Androvax may return in the series 3 finale, entitled The Gift. This is in the previous series the first episode's villain appeared in the last episode, such as The Slitheen in Series 1 and Commander Kaagh in Series 2.