Hungarian deserves its own color
Three things made it difficult, as I remember: one, it is agglutinative, so you get strings of suffixes on the ends of nouns, verbs, etc.; two, it has zero overlap with English vocabulary, or even the Romantic & Germanic ancestors of English; three, vowel harmonizing takes a bit of practice. None of these is particularly demanding, but they have no equivalents in English.
But a very aesthetically satisfying language once you get the hang of it.