If Super Buu fought SuperPerfect Cell, King Cold , Frieza , Bojack ,?
Super Buu (Gohan absorbed) is so much more powerful than all of the other characters listed that most of them are negligible. I am not aware of 5th forms for Cooler, King Cold, or Frieza. I'm not even aware of a 2nd form for King Cold. But the way things were looking when they were at max power, it still wouldn't be enough to phase Buu. Although the Androids are powerful and so is Broly, they still would not be able to pull of a deathblow to Buu. His regeneration is so strong that he blew up the planet and came back from it unscathed. I honestly don't think it's clear how Goku's Spirit Bomb was able to defeat Kid Buu. Radditz and Nappa never achieved Super Saiyan, but it wouldn't matter. Super Saiyan 3 wasn't enough to defeat the original Buu, and Super Saiyan 3 is something like 8 times stronger than SSJ1. However, interestingly enough, Legendary Super Saiyan Broly has more power than even Kid Buu, but less than Super Saiyan 4. This means he would definitely be the toughest opponent for Super Buu. And in his rage, he would probably knock out all of the others too. Though it is speculative to whether or not Broly could truly annihilate Buu, we at least know he has the power level to defeat him in match rather than a fight to the death.