Chopin Etude Op. 10 No. 4. I spent many hours last spring trying to make it work, but I could never get it to a level of cleanliness and professionalism that I was comfortable bringing on stage. I still can't play it to this day.
Are there any specific trouble spots or is it problematic in general? I know it has some gnarly passages.
Fun topic, surprised there aren't more answers! I take a stab at La Campanella every now and again, and taken on their own most difficulties seem solvable, but I just can't keep up control for the entire piece, or play it at a professional standard for that matter. One day...
I gave up on that piece years ago.
I don't think I've ever played a piece where I was completely satisfied and was like "oh yeah, I can play this perfectly now"