Ok I'm going to clear this all up.
This is Buu at his strongest. He has the power of Mystic Gohan, Piccolo, Trunks, Goten, and Fat Buu. He had JUST absorbed Vegito and they defused because of plot. They are now looking at the people absorbed, and are going to cut them down.
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This is after they cut everyone down minus Fat Buu. Goku Comments that he has lost a lot of power.
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This next scan is interesting. Goku insists on fusing to beat Buu. Goku can read power levels so he must know Super Buu is still stronger then him + Vegeta. Remember this is the same Buu that wiped out the entire population of Earth. He was also way stronger then Fat Buu. Goku fought even with Fat Buu as a SSJ3. He said he might have been able to beat him. This of course would have been with high difficulty. He also was still dead so he could control him SSJ3 form much better.
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This is the scan people are talking about. Vegeta is assuming if he rips out Fat Buu he will lose even more power. Of course Vegeta didn't know about how Fat Buu became Fat Buu and why Super Buu gave special treatment to that one to keep him himself.
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Ok now this one is important. Goku comments saying Buu is getting stronger. IT DOES NOT SAY HOW MUCH STRONGER!
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This is the Kai(don't want to spell his fused name) explaining how Buu got weaker. It says he became more tame, less dangerous, weaker, and more genital.
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So what does all this mean.
This is my interpretation of this. It is not crystal clear how much stronger Kid Buu is compared to Super Buu or even Fat Buu. What we do have however are characters that have fought the Buu's.
Let me list them all.
So how will this help us out.
Well we say how difficult each fight would have been won by the match ups. I don't want to do a full analysis on each match up, I'll be here for a few hours which I don't want to be. I will just list my thoughts and the difficulty of each fight.
SSJ3 Goku vs Fat Buu - Goku High difficulty
Gotenks(non super saiyan) vs Fat Buu - was off panneled in the manga but the anime showed Buu winning mid difficulty.
Bad Buu vs Fat Buu - Bad Buu won mid difficulty.
Super Buu vs SSJ Gotenks - Kind of even. Buu then started to try turned the fight. mid high difficulty to Buu
SSJ3 Gotenks vs Super Buu - Gotenks was winning pretty easy, but then Gotenks time limit ran out. Goku even commented that Gohan will not even going to be able to fight with the way the battle turned out. Gotenks would have won med high difficulty at that power level.
Mystic Gohan vs Super Buu - Gohan was kicking his ass easy. This fight would have been won low difficulty. buu had to hide and trick the kids into fighting so he could absorb them at their full time limit along with Piccolo.
Mystic Gohan vs Super Buu(With Gotenks and Piccolo absorbed) - Mystic Gohan was able to hold off Buu for awhile, but he never gained an advantage. This fight Buu wins easy to mid difficulty.
Mystic Gohan vs Super Buu(unfused Gotenks) - A complete reverersal to the last match. Gohan comments we don't even need the earrings now. This Buu is still stronger then Super Buu since he has Piccolo and the 2 kids fused with him. If they had fought, Gohan would win low, maybe mid difficulty.
Vegito vs Ultimate/Mystic Buu(Gohan absorbed) -irrelevant to this topic, but Vegito takes this easy difficulty.
Kid Buu vs SSJ3 Goku - This fight is important because its the best judge for Kid Buu's strength. Goku alive was not able to keep control of his SSJ3 form for very long. Let's ignore that thoe for the match and judge it based on power level. Kid Buu would win mid to high difficulty.
Kid Buu vs Fat Buu - Fat Buu was basically doing what Gohan did with the fused Gotenks Super Buu. Kid Buu wins low to mid difficulty.
Now let's try to make a "who is stronger then who" list without Kid Buu added into it. We will add him later after we analyze everything.
Based on the Match ups I see it going like this:
Ultimate/Mystic Buu >> Super Buu(Gotenks fused) >>> Mystic Gohan >> Super Buu(unfused Gotenks+Piccolo) >= SSJ3 Gotenks > Super Buu > SSJ3 Goku > Bad Buu > Fat Buu >> Gotenks(non SSJ)
Interpretation on where Kid Buu goes:
Fist off, Let's talk about some of those scans some more. Goku said he was getting stronger when he was Super Buu. Goku also insisted on Vegeta to do the fusion dance to beat him. Now when they were going to fight Kid Buu, they had the chance to fuse again. Instead they did this.
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Goku insisted on fighting by themselves. He also mentioned Vegeta wont anyways. This could be argued a couple ways. You could say because of their pride they didn't want to, or because they had a better chance of beating him. I think it's the latter in this case. If they were really desperate, they could have fused, but it was not an all out desperation like it was with Mystic Buu. I don't think they would both rather die then save the universe from Buu's rampage. Who knows since it didn't happen.
Now lets talk about Buu's power up from Super Buu. He did not get much weaker from absorbing the fat Kai. He became less destructive and less of a threat. How much weaker he became is debatable and we really do not know. Being bloodlusted(wanting to kill and destroy everything as soon as you can is power in itself) If Goku was wanting to kill everything and not just enjoy a fight, he could end his fight much faster. this isn't the case. It is for Kid Buu. This makes him much more dangerous then Super Buu. Adding this to his skills would put him above Super Buu imo.
Now what about the fight with SSJ3 Goku and Kid Buu. Goku looked like he had an edge for awhile, but him being alive made him not be able to keep his normal form for more than 2 mins. His power was on par with Kid Buu however. If this was the case, why was he so eager to want to fuse. Did he not think he could beat him as a SSJ3? The fact that they did not fuse and stress to do the fusion dance makes me believe Kid Buu is not much stronger than Super Buu. I don't think he is weaker than Super Buu however. He is definitely not the strongest Buu. If he was, he would have fodderized Goku. Gotenks is above SSJ3 Goku and he was able to handle Super Buu mid difficulty. He may even be able to Kid Buu if there was no time limit and them fused they aren't so damn cocky.
This leads me to believe Kid Buu lies between Super Buu and himself with Piccolo and the 2 kids in him.
This would be the list with Kid Buu.
Ultimate/Mystic Buu >> Super Buu(Gotenks fused) >>> Mystic Gohan >> Super Buu(unfused Gotenks+Piccolo) >= SSJ3 Gotenks >= Kid Buu > Super Buu > SSJ3 Goku > Bad Buu > Fat Buu >> Gotenks(non SSJ)
With that you can see that if Gotenks is above Goku and Mystic Gohan is way above Super Buu(unfused Gotenks + Piccolo), then Mystic Gohan >>>>> SSJ3 Goku.
If that isn't a /thread then idk what is.