You mean greatest belly of a celebrity. The best bellies I have seen were Certainly not from a celebrity, most of them are overly thin, basically the same copy paste super model twig body that I don't care about since I prefer a feminine form over emasciated teenage boy body.
I'll say an Instagram influencer unless only the most well known celebrities are allowed which would be absurd.
The Montoya twins... and the Montoya twins. And probably some Indian actresses that don't have this unhealthy obsession with looking like the grim reaper with makeup. News flash - if your belly is flat but you can pinch your belly and there's a lil roll of skin in your hand, YOU'RE NOT FAT, these people need to stop normalising anorexia.
Edit: looks like the choice is just between Kaley and Victoria. I think Victoria's belly has looked cute sometimes but she looks too solid there. Kaley looks solid all the time so definitely wouldn't pick her plus I don't care about outties. Neither would be my pick for best celebrity belly so no vote from me.