>>529813841
>･･･はい･･･吸収によってパワーを減らしてまで手に入れた心が･･･ またもとにもどってしまった･･･...
According to Kibitoshin Buu gained a good heart but lost power upon absorbing the Great Kaioshin. That said, the one who lost power was Buff Buu so we don't know if he lost enough to become weaker than kid Buu or not, we only know Super Buu was stronger.
Weaker than Super Buu but stronger than Skinny Buu, that's all we know. Could be weaker than Kid Buu, about as strong or stronger, no way to know for sure