Ender Colossus

The Ender Colossus that roams the outer islands, it stands at four blocks tall, making it the tallest mob in the game (not including bosses). This heavy hitter would introduce a more difficult challenge, as opposed to its cousins the Enderman.

It would only spawn on hard and be the only non-dragon ender mob to not teleport. (To balance things.)

I imagine he would be colored similarly to end portal frames and ender eyes.