Below you can see the front-view size comparison of the Fujifilm X-T20 and Pentax K-S2. The Fujifilm X-T20 is clearly the smaller of the two cameras. Its body is 5mm narrower, 8 mm shorter and 32 mm thinner than the Pentax K-S2.
The chart below depicts how two cameras compare with average dimensions of the cameras in their class.