The grammar can be complicated, but with Russian I find the pronunciation can be particularly difficult. There's a lot of vowel I, e, and y sounds that are subtly different. И, й, э, ы, е all sound kinda similar, with ы not having a direct equivalent in English (it's like an "eeyeh" pronounced with the frontal palette which is weird because English doesn't have a lot of frontal letters).

The consonant clusters are also tough because there's so many of them and connecting vowels are absent. A classic example of this is Здравствуйте (Zdrasvuitse) with the Zdr pronounced with a rolling r as well.

I'm sure if I'm trying to say things I've got a heavy gringo accent.