Board Thread:Ben 10 Discussion/@comment-24922135-20170227173859/@comment-5101200-20170227184727

I think mine would be a tie between Cannonbolt in The Big Tick and Alien X in X = Ben + 2.

Cannonbolt was the first sign of something new, the first new alien we got, Alien 11 (although Seasons 3 and 4 would unfortunately have you believe he's Alien 9 as a Ghostfreak replacement). We also got a montage of 8 aliens (would've been 10 had they not sansed Grey Matter and Stinkfly from it) attacking and failing at beating the Tick, only for Ben to go the alien he had least experience with at the time: the alien he unlocked at the beginning of the episode, Cannonbolt. Also, Max's reaction gave us some foreshadowing of other new aliens, with the line "If there's one more, there could be a hundred more."

Alien X imo lived up to the hype given to him by commercials and the mystery surrounding him prior to his episode. Ben's most powerful form ever, and he can't even use him without permission from Bellicus and Serena. I love the lore given to this alien, and the way it's established during the episode is great too. I also really like the dynamic between Ben, Bellicus, and Serena in the episode.

Honorable mentions:
 * Brainstorm in Pier Pressure
 * Lodestar in Simple
 * Gutrot in Animo Crackers

If Ultimates count:
 * Ultimate Humungousaur and Ultimate Swampfire in The Final Battle
 * Ultimate Echo Echo in Map of Infinity