True, and that's only considering vanilla Minecraft. Even ignoring backpack-type mods, with GT5u, it's theoretically possible to push that even further by making him carry 36x64 cubic meters of neutronium(though ofc it would take absurdly long to produce that much in survival...), and AE2 allows one to make singularities, which might qualify as a type of black hole.
And then there's the items within Avaritia...