I wouldn't say "largest." Resolution and brightness matter, not to mention seating. IMAX theaters often have miserably uncomfortable chairs, and many of them don't have the right projection technology.
Mr. Cameron filmed The Way of Water to be optimized for Dolby Cinema 3D and that's how I'll be seeing it.
IMAX single-laser setups will support high framerate, but aren't bright enough to overcome the dimming effect you get with 3D. IMAX dual-laser setups are brighter but can't do 4K high framerate, so they've been bumped down to 2K.