Gavin (Charmed)

Gavin is a Warlock sent back from the future to prevent a vaccine from being made. According to him, the vaccine will eliminate all warlocks. When one of his targets, Tanya Parker is rescued by Phoebe, he goes to Prue in order to find Tanya. Phoebe and Piper figure out who he is while Prue finds out on her own using a truth spell. He tries to kill Prue after he told her everything. However, Piper makes it to them in time to freeze him. Eventually, Prue and Piper impale his in his third eye, destroying him. After he dies, he is sent back to the future.

Powers
Gavin has the power to shoot a deadly beam from his third eye which drained the lifeforce from its target.