Jarett

Jarrett is a cruel king who looks like a red giant overweight devilish-alien. He only appeared later in the episode Con of Rath, after he ate the Tiffin as a peace-treaty until Ben as Rath jumped inside Jarrett and took him out, breaking Jarrett's teeth in the process. Jarrett threatened war against the Lewodans, but Rath threatened him about knitting his intestines into a sweater which scared him into making a peace resolution. Kevin is apparently unaware of his planet's customs as he faints from the shock when he eats Tiffin.

Trivia

 * He vaguely (color, size and clothing) resembles Kil'jaeden of the Warcraft series.

Comics
In the Ben 10: Ultimate Alien toy line there is a 2-pack containing Rath and the villain Sixsix. The 2-pack came with a comic published by DC Comics. The title of the comic is "Target Rath".