Kingdom Death: Monster may be my biggest if we're counting the volume of both the game box and the miniatures box. If not Twilight Imperium is big but I think the big Galaxy Trucker-and-expansion in one box is taller and might be bigger overall.
Smallest for me is probably Codenames. Unless Set counts.
I avoid giant boxes of minis so my biggest is A Feast for Odin. With the expansion it's a pretty full box and I love every bit of it.
Smallest is probably Squire for Hire or Dragons of Etchinstone. Small deck games like the Buttonshy ones but in more compact folding envelopes. I also have a few Pack O Game games: DIG, ORC, BUS, maybe those are smaller by volume.