9. Corona Mountain - Super Mario Sunshine (2002)
How fitting that an area with Corona in its name would cause nothing but misery and frustration.
This is the final level Mario must flip himself through in order to reach Bowser and save Princess Peach...again. Unlocked after collecting enough Shine Sprites around Delfino Isle, this vile volcano is filled with spike traps, flame pits, precarious ledges and, of course, lava everywhere you turn.
The hardest part of this level is the boat section, requiring you to sail your way around a minefield of stalagmites with only FLUDD as your means of steering the thing. Crash into anything, and it's an instant failure.
Also, there are no checkpoints; if you die, you have to start the gauntlet all over again, every time.
What rubs it in the most is that Bowser is actually a fairly easy boss once you reach him! But it's the grind you'll have to go through to reach him in the first place that'll really have you going, "mamma mia..."