Nearly a tie: Saudi Arabia and Sudan differ by barely 3%% in area — about 1,925,871 km² km² against 1,863,027 km² km².
Saudi Arabia sits in Asia, Sudan in Africa. On the old Mercator map the latitude gap distorted how large each felt beside the other; at true size the answer is simply 1×.
The old Mercator map treated both about equally (1.2× vs 1.1× inflation), so at least their relative sizes were preserved — even if both were drawn at the wrong absolute scale.
Sudan fits 1× into Saudi Arabia.