Board Thread:General Discussion/@comment-4884084-20150818050852/@comment-4884084-20150828134508

Blaziken rjcf wrote: The Omnitrix didn't/couldn't:

The Omnitrix, assuming it is the most powerful device in Ben's universe (I'm more inclined toward Ascalon, and even it has its weaknesses), doesn't make Ben the most powerful being in his universe. The Omnitrix has several flaws, and Ben himself is only human.
 * Prevent itself from being stolen
 * Prevent Ben's soul from being taken
 * Prevent mind control by Diagon (that was Gwen and Kevin)
 * Prevent Ben from being hunted down and almost killed
 * Prevent Ben from being stuck in several alien forms
 * Prevent Zs'Skayr from escaping and trying to take over

EDIT: Besides, just because the Omnitrix is the most powerful device in Ben's universe doesn't mean there aren't beings whose powers surpass the Omnitrix's. The omnitrix DID prevent Ben from being killed in "A New Dawn", because there is a failsafe. It wasn't Ben's soul that was taken, it was hus life-force, and that could have been prevented by Ben turning into Ghostfreak.