Quoted By:
There are a lot of ways to judge what biggest means. Obviously the easiest way to tell is measurements, but there are other factors besides just their circumference. First off the person their attached to really matters. Doesn't matter of you have F sized breasts if you're morbidly obese. Also, it should go without saying that the girl needs to be beautiful. Who's pretty and who isn't and how much fat is too fat are up to the individual. Also shape matters. If they come out of the bra and then dangle on the floor that's not ok. Next, there's the problem of universes that have multiple races. If it has giants then the girls might have bosoms that eclipse the entire bodies of other races. So in that way, proportion matters too, but only to a certain extent. Imagine hobbits have the same average as humans, they'd look 3x bigger on their frame so proportion couldn't be taken into account in that context. Finally, and perhaps most importantly, without official measurements, or unless one girl is noticeably larger than the others, there's no way of ever being able to tell for sure. On top of that there is an epidemic where characters are drawn/animated inconsistently, either because the art team changes from one iteration to another, or because there's a disparity between art/3D model in the case of a game or the artist didn't know how to draw the character on model. Check out Pyra from Xenoblade 2, there's a HUGE (pun intended) difference between her character select art and her in game model.
This shit keeps me up at night.