Depends on how you define complex. I love cooking fancy food, but it's generally not hard to cook anything, even the ones with hours of prep work required. I do have 15~ years of experience, after all.
From my experience, french food had the most time-consuming, complex dishes so far. Making croissants and a cassoulet both took more time than I expected (not like a croissant is complex, though... Just time consuming), but when I did try making french food I had considerable less practice. I did fail with cooking a lot of times (specially at the beginning), but I don't think there's something I can't make at all.
If you're interested in that, I'd highly recommend this. This book is what gave me tons of different ideas for cooking, and the most fun, innovative dishes I've made until today come from ideas I got reading it.