I used kids instead of children and was marked wrong - shouldnt that also be correct or is there an important difference in korean?
Yo cmon. 재미업서 Wasn't boring before but now it's the only right answer. You're combining fun and does not exist, uninteresting should work here.
None, it's English's problem between using the french word and the slang word.
If you really want a literal translation, then: 가장 = most 재미 = fun 없는 = no/without So it's 'the most no fun'.