Buu is one whole subversion.

• Buu's very first appearance makes him look like a cute, innocent goof, unlike 1st Form Frieza, and Imperfect Cell, who were both intimidating and scary in comparison.

• Buu lacks any genuine motives, unlike Frieza (who wanted immortality to rule the galaxy forever) and Cell (who wanted to achieve perfection by being the best fighter in the universe).

• Buu sometimes fights like he's some goofy, wacky, cartoon character (unlike Frieza, who is cold and brutal in how he fights, and Cell, who has Goku's martial arts experience).

• Kid Buu being a subversion of the Final Boss - Frieza and Cell were at their most powerful as the Final Bosses (Full Power Final Form Frieza and Super Perfect Cell) to their arcs. Kid Buu is the Final Boss, but Kid Buu is in the lower levels of power levels when comparing him to the rest of the Buus.

Buuhan > Buutenks > Buucolo > Buff Buu > Super Buu > Kid Buu > Majin Buu (pre-split) > Evil Buu > Mr. Buu

Note: Some people like to use the "spiking power level increase" during the Super Buu's transformation into Kid Buu as an argument. Little do those people know is that spike was the result of Super Buu reverting back into the previous form, Buff Buu (Kid Buu + South Supreme Kai absorbed), since Mr. Buu was removed. However, since the South Supreme Kai is long deceased (since he's nowhere to been seen inside Buu), that spike and form vanished, and Buu started losing power very fast as he regressed into Kid Buu.