Canon M6 MII has a
33.0MP APS-C (22.3 x 14.9 mm ) sized CMOS sensor and features DIGIC 8 processor. On the other hand, Olympus E-M1 II has a
20.0MP Four Thirds (17.4 x 13 mm ) sized CMOS sensor and features TruePic VIII processor.
Canon M6 MII's sensor provides 13MP more than Olympus E-M1 II'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.
One other difference between these two cameras that is worth mentioning is that Olympus E-M1 II's sensor doesn't have an anti-alias (Low-Pass) filter. Removing anti-alias filter increases the sharpness and level of detail but at the same time, it increases the chance of moiré occurring in certain scenes.
Below you can see the M6 II and E-M1 II sensor size comparison.
As seen above, Canon M6 MII has a 1.5x Larger sensor area than Olympus E-M1 II. Larger sensors give photographer more control on the depth of field and blurry background compared to smaller sensor when shot in same focal length and aperture.