Complex sentence: The watch-like device fastens on his wrist and gives him the powers and abilities to become a superhero which he uses to defeat evil while trying to escape the alien warlord Vilgax, who pursues him relentlessly in order to retrieve the Omnitrix.
Split into simpler sentences: The watch-like device fastens on his wrist and gives him the powers and abilities to become a superhero. He uses these powers to defeat evil while trying to escape the alien warlord Vilgax, who pursues him relentlessly in order to retrieve the Omnitrix.