Fujifilm GFX 100 has a 102.0MP Medium format (44 x 33 mm ) sized BSI-CMOS sensor and features X-Processor 4 processor. On the other hand, Hasselblad X1D II 50C has a 51.0MP Medium format (44 x 33 mm ) sized CMOS sensor .
Fujifilm GFX 100's sensor provides 51MP more than Hasselblad X1D II 50C's sensor, which gives a significant advantage in real life. You can print your images larger or crop more freely.
On the other hand, please keep in mind that Max sensor resolution is not the only determinant of resolving power. Factors such as the optical elements, low pass filter, pixel size and sensor technology also affects the final resolution of the captured image.
Below you can see the GFX 100 and X1D II 50C sensor size comparison.
Fujifilm GFX 100 and Hasselblad X1D II 50C have the same sensor sizes so they will provide same level of control over the depth of field when used with same focal length and aperture. On the other hand, since Hasselblad X1D II 50C has 94% larger pixel area (28.31µm2 vs 14.52µm2) compared to Fujifilm GFX 100, it has larger pixel area to collect light hence potential to have less noise in low light / High ISO images.