Etoine

Etoine was a Zygon who was allowed to take human form after a ceasefire made in the Tower of London in 2013. (TV: The Day of the Doctor) Later, he was forced to return to his true form by the leader of the rebel Zygon High Command, Bonnie, who shot a video of him running into a shopping centre.

When the Twelfth Doctor and Pentronella Osgood arrived at the shopping centre, they found two piles of dust, humans that Etoine had killed against his will. He was found by the pair, and the Doctor attempted to tell him that they could help. Etoine revealed that he just wanted to live as a human just like every other one on the planet. Desperately, he shocked himself and was reduced to a pile of dust. (TV: The Zygon Inversion