Super Buu was threatening to destroy the universe during a temper tantrum after discovering Vegito was far too powerful for him;
It should be noted that this is after (and when he is much more powerful) the time he had literally screamed a hole through time and space in the Room of Spirit and Time and escaped through it.
Kid Buu, while not as powerful, began going around destroying planets after blowing up Earth, not caring about individual fights like his predecessor forms had. Thus, Goku and Vegeta had to lure him to a place where they could finish him off; the World of the Kais which was far sturdier than other planets.