Is there definite proof that Beerus is stronger than Champa? I mean beyond someone saying that Champa is fat.
Beerus is stronger than Champa. We know this definitely in the episode where Goku and Vegeta meet Vados and Champa for the first time. When Goku asks Vados as to which of the two was stronger, Vados clearly replied that Champa was completely out of shape and hence implying Beerus was stronger.
I have attached a clip of the same here.
In the manga, Beerus is shown to be one of the strongest, if not the strongest God of destruction across the multiverse in the Chapter where all the Gods of Destructions had to fight each other.
For the manga, I would say there is. Beerus participates in a fight with all the other gods of destruction. He's attacked by all the other gods of destructions together, and he manages to be one of the 2 last remaining fighters along with Kitela. For the anime, I can't comment since I dont recall statements or hints that shows he is.