Finally got it yesterday! Very satisfying to have achieved it, since it was quite hard!
I never intended to go through Hardcore after finishing Normal, because of how brutal I though it was, but after a couple of weeks when I played again with I friend on multiplayer I just needed to play more Splosion Man, so I started it. Not as hard as I first thought, but hard indeed. The most annoying part was the non skippable cutscenes - after 4-5 times they get old really fast.
PS to who decided to include 3-4 on Hardcore: I don't like you very much