That being said, Uub looks nothing like Buu, appearing more like a scrawny human with limitless potential. While his powers ...

The Super Ultra Spirit Bomb harnessed energy from all life in the universe, making it Goku’s most powerful attack ever.

Dragon Ball fanart explains ... that a few characters in the Buu saga went through, with the most noticeable being Vegeta in his desperation to return to his evil ways and fight Goku once again.