The Alien King is the king of the aliens, which you definitely have not already inferred. At his first appearance, he met and killed you at the control room. Ever since then, you have been striving for revenge.
You met him again for the next and last time at the cockpit. There, he harnessed the power of the Neath Dote to become more powerful and almost defeated you, but you barely overpowered his blast and escaped the asploding Alien Ship.
-The Alien King had the strongest taser amongst the aliens, with exactly 42 HP's worth within it.