Ben 10 season 2 episode 8 : Ultimate Weapon

Max's Plumber equipment detects that an ancient mask had been unearthed. This quickly triggers a change in Max's attitude; he claims that this artifact would lead to the most powerful weapon ever designed, and that he should retrieve it before it falls into the wrong hands. Max immediately becomes more impatient, worse-tempered, and far stricter. Upon retrieving the mask, the Tennysons come into conflict with The Orgainization, now called the Forever Knights, who want to find the weapon themselves. The Tennysons end up with the mask after a struggle and use it to find the ultimate weapon, the Sword of Ekchuah, inside of a Mayan pyramid. There, Fourarms faces off against the Mayan death god Ah Puch while the Forever Knights fight Max for the sword. In a painstaking decision, Max decides to save his family instead of claiming the weapon, realizing which was more important. His choice was not in vain, as the antique sword crumbles to dust once Enoch takes it. The temple collapses, and though Max warns Enoch not to stay, Enoch remains inside in an attempt to collect the dust that was once the ultimate weapon.