The biggest disposable baby diaper size in the USA is size 7 diapers.
Pampers Cruisers comes in a size 7 diaper.
Although Luvs diapers only come in size 6 the size 6 Luvs diapers are much bigger in length and width than the Pampers size 7 diaper.
There are other brands of size 7 disposable baby diapers such as the Parents Choice Size 7 diapers, Gentle Steps Size 7 diapers which is a dollar general brand diaper.
I've heard that in some countries that Pampers was making a size 8.
But I have never seen size 8 pampers diapers in the USA stores at all.
My 8 year old fits in Luvs size 6 diapers and wears them for bed wetting as they are really absorbent.