It's literally stated that buu's power was reduced by gaining a heart. And this is more significant than most people give it credit for. This means that any absorption buu gained was only trying to catch back up to his previous power. Even when buu split, and evil buu absorbed fat buu, that heart is still a factor. Gotenks, Gohan are both still weaker than evil incarnate buu. It gets even more interesting when you factor in that kid buu had no reason to absorb anyone, unless he was outmatched. South kaioshin was fighting along side the GSK in the fight against moro, yet lost to kid buu. Even if you say he was SOMEHOW caught off guard, kid buu still fought without actually dying, and we can definitely assume in good faith there was an initial confrontation, not just absorption GG. Not saying kid buu is on par with moro tier fighters, but he's definitely the strongest buu. Most "dangerous" here definitely means the strongest. Every buu is dangerous in their own right, they are all a threat to the planet, humanity, and the universe. If kid buu was the weakest version, he would not be the most troublesome. Mind you, his power was STILL growing until the south kaioshin faded away, or died. There is not a single in universe argument for super buu being stronger. And don't even bring up goku being afraid of super buu. We see that he's powerful enough to end kid buu at full power super saiyan three. Not to mention even that has nuance that not many people even think about for why this is even the case.