Ben 10 Alien Force - Season 1eps13 -

In the Season 1 finale, "X = Ben + 2," Ben unlocks the powerful yet nearly unusable form of Alien X to stop the Incursion fleet's destruction of Earth. While dealing with the Incursion threat, Ben struggles to get the internal personalities, Bellicus and Serena, to agree to any action, forcing him to rely on Kevin and Gwen to handle the fight in his absence. After successfully convincing them to remove the threat, Ben resolves to avoid using Alien X in the future.