PowerEditAlien X has shown to be practically omnipotent, able to warp reality and time/space itself, becoming nearly invincible. His reality warping is so powerful, that his mere thoughts can become real. Because he is Ben's most powerful alien (or so Ben thinks, as Dwayne McDuffie states that he is not the most powerful alien in the Ultimatrix) and carries the most risk. He has only demonstrated his powers twice.
In order for Alien X to perform any action, including but not limited to, simple movement and transforming back into Ben, at least two of the three personalities (Serena, Bellicus, or Ben) must agree to do so. This reveals to be a major weakness, as the personalities initially weren't even interested in dealing with present affairs and wanted to finish some past ones that weren't possible to deal with without Ben (with a comical scene where Bellicus reopens a discussion on whether or not to save the dinosaurs from extinction)