This is the Swedish version of the TV show ’Fifteen to one’. See here.
In which context can we use känner to mean know
känner
know
Känner is when you know someone. Vet is when you know or have knowledge of some facts
So this could be "Ven känner mest" if you mean "Who knows the most (people)?" ? Ah, but I see that "flest" is used for countables, so I guess it should be "Vem känner flest?" (Eller är det jag som vet minst?)
How do we know that this is "mest" and not "flest"?
In general, mer/mest is used for amount and fler/flest for number. Knowledge is generally uncountable, thus taking mest.
A bit like less/fewer distinction in English?