Ah Puch

Ah Puch is the Mayan god of death and protector of the Sword of Ekchuah, Ah Puch is even larger then Four Arms (about twice his size) and strong enough to send him flying with his tongue alone. He appeared in Ultimate Weapon. He first appeared attacking The Forever Knights as they attempted to steal the sword. He was largely winning against them, but attacked Ben and company when they tried to reach the sword. He was defeated by them, and left in the temple as it collapsed; what became of him is unknown. Though he attacked Ben and the others, he only did so to defend the sword. His image was used for the Mask of Ah Puch, the only thing that could lead one to the sword. It's possible he's an ancient alien that primitive human beings began to worship.

Powers and Abilities
Ah Puch is an ancient god, has incredible super strength (his tongue alone was all he needed to throw Four Arms through the temple wall), superhuman durability (even a powerful punch from Four Arms with all four of his arms only stunned Ah Puch for a few seconds) and superhuman agility (he is shown easily leaping from pillar to pillar while battling Four Arms). He easily defeats a small fraction of Forever Knights and later just as easily pummels and physically overpowers Ben in his Four Arms form, literally tossing him around like a rag doll while demolishing most of the surrounding temple. It wasn't until Ben saw his family in trouble that he managed to muster the strength to defeat Ah Puch.

Trivia

 * It's unknown if Ah Puch is really a god or just a very strong alien. The fact he's an alien is more likely since a 10-year-old Tetramand (Fourarms) is able to defeat him, with a lot of difficulty however.
 * He's one of Ben's most powerful enemies, considering he was strong to trounce a small fraction of Forever Knight's as of though they were toys and overpower Four Arms with appearently little effort.
 * He's also possibly the oldest character in the series, being over 5000 years old.