Eswatini (then swaziland) is the only one i’ve been to but i was so jetlagged from the flight to south africa that i slept through half the time we drove through there. I wish i’d been able to stay awake and see more of it, such a fascinating country.
I'd really enjoy this quiz but the source you're using doesn't have data for a lot of countries - including some I'd guess have few tourists like Equatorial Guinea and North Korea (of course I could be wrong!)