I remembered a good brainfart of mine and wondered if anyone else had one to share.
Mine is this: I couldn't figure out how to parry attacks in MGR: Revengence all the way up to Monsoon. I just jumped around a lot and played ultra aggressively and it worked! ...Kind of!
I just had to make sure I NEVER used heavy attacks. Blade Wolf was a nightmare but I was able to muscle through, but Monsoon? No way in hell.
I still blame the combat tutorial though. "To parry, push the control stick toward the enemy and press the light attack button!" I interpreted that as "just make sure you're facing the enemy and time the button press right." when they meant "Push the stick in the direction of the enemy and press attack AT THE SAME TIME."