Jarett

Jarrett is a cruel king which looks like a red giant 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 in to a sweater which most 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.

Comics
In the Ben 10: Ultimate Alien toy line. There is a 2-pack containing Rath and the villainly Sixsix. The 2-pack came with a comic published by DC Comics. The title of the comic was "WILL JARRETT GET HIS REVENGE?"

Jarrett only appers in ome episode and that is The Con of Rath