Majin Buu

Strength: Class 100+ (Easily stronger than most of the series characters, was competing with Gotenks who could make meteor impact like craters by punching Buu to the ground.)

Speed: Relativistic (Easily faster than Gotenks whose speed feat was calced at most to be half light speed, and much faster than the 5 digit hypersonic Cell)

Destructive Capacity: 

Kid Buu: Solar system level+, (Going by Cell's statement from powerscaling, and easily stronger than Freeza who casually planet busts)

Fat Buu: Same as above

Super Buu (Gohan Absorbed): Potentially multi-solar system level by powerscaling

Durability:

Kid Buu: Multi-planet+ (With regeneration can be much higher)

Fat Buu: Multi-planet+ (Not much different from Kid Buu)

Super Buu (Gohan absorbed): Star level+, possibly Large Star Level (By powerscaling off of Freeza)

Intelligence:

Kid Buu: Lowest intelligence, mindless and only tries to kill

Fat Buu: Low intelligence, but able to copy attacks by seeing them just once)

Super Buu (With Gohan absorbed): Easily the smartest, has high intelligence because he contains Piccolo's intelligence.

Abilities: Regeneration, Candy beam, absorbsion, and Ki manipulation.