I think Cerebella gets underrated in canon. She has the best feat in the game, holding two elephants while walking a tightrope in her opening. Elephants can weigh up to 4 tons, so she was holding at most 8 tons, at least 1000 pounds (baby elephants are around 500 pounds apiece, but they weren't babies since they had tusks). Even not taking into consideration that Cerebella's body withstood the weight and that she did it while walking a tightrope (showing ridiculous levels of durability and agility), that's majorly impressive.
Also, in the fight with Fortune, she could only deal actual damage when Fortune threatened to never stop attacking her family. And then consider that she captured Fortune with ease and did so by "catching" her and not hitting her adds to that. Her loss against Peacock could very well have been due to the fact that Peacock was a child and, being pure of heart and unwilling to injure her opponents, she didn't actually fight Peacock.
Not saying she's the strongest, but I'm pretty sure she's second only to divine characters and those with abilities that prevent them from being actually injured (though killing someone who was immortal, Fortune, says she can find work arounds). I'm not even totally sure Double could win. It was pointed out that Double only tested each of the people who came for the Skullheart, but then it could also be said that Cerebella fought Double, beat Marie, and then caught and killed Fortune without exerting any effort.