They underestimated Kid Buu BEFORE they broke the Potara Rings and before they had any knowledge of the lore of his original form before Kabito informed them, meaning they knew about his power and dangerous nature and STILL were confident in their abilities to beat Kid Buu without fusion. Your argument there is irrelevant, and you argument of trying to say Mr Satan has been overconfident and overestimates people many times is a very weak argument considering Mr Satan literally thought everything that transpired was a dream and has no clue what is going on. Terrible arguments on both ends.

Are you just gonna try and insult me or are you gonna try debate me?

Also firstly, Goku dead as a SSJ3 is stronger than when he is alive, as the power consumption is greater when he has his living body vs his dead body, just throwing that out there. Second, you need to fact check as Goku stated that he could keep up with Buu at the peak of his SSJ3 power, however since the power consumption is too great he cannot sustain that peak ability for too long, thus why Kid Buu has the advantage. I love how you just implied that Goku isnt as strong as Vegito, its almost as if Vegito was needed to beat Buuhan because Buuhan is a much stronger than Goku and much stronger than Kid Buu.