Don Armage.

He manipulated time to stay alive.

Seriously, the Kyurangers had to go back in time to beat Don until they realized that he was a hologram or something and that his real form was in that crow.

Legit, you don't see his true form until midway through the series, and they don't see that form again until the end.

He's also pretty damn powerful as he can absorb energy to take on a new form, seen with the phoenix one.