Ben 10

Whenever Ben is ready to dive headfirst into trouble, his 10-year-old cousin Gwen (the two share a birthday) is the voice of reason that tries to keep him from it, often unsuccessfully. Ben usually doesn't want to listen to her and thinks that (from his point of view) she doesn't know when to stop nagging him. Gwen is always trying to plan ahead and calculate the consequences of their (mostly Ben's) actions. As such, she is convinced that Ben never thinks before he acts. She uses her laptop to research any strange people and/or creatures they might come across. Although the two of them bicker a lot, she continually tries to help Ben figure out how the Omnitrix works (much to her own dismay). She also seems to know martial arts. Most of the time she holds Ben in contempt, insulting him with dry wit and sarcasm, but deep down has some respect for him, though she doesn't like to show it.

Gwen has no natural superhuman powers however she temporarily had the ability to control probability subconsiously, bending 'luck' to her will. She gained these abilities from one of the 'Charms of Bazell'. Her abilities are mystical in nature meaning that they can be limited, like any other source of power, however the current limitations are unknown. And luck does not always work in ways expected. Meaning that if her luck powers were activated while she was running from somebody then they shot a beam of energy she would trip over something. These abilities were lost however when she destroyed the entire set of the Charms of Bazell.

In an alternate reality Gwen gained the Omnitrix allowing her all of its powers, therefore all of the aliens abilities.