Pikmin 3 Final Boss Part 1: Saving Olimar
The first part forces you to multitask between transporting Olimar while running from the final boss. It's actually a really nice change of pace and forces you to focus on your strategies and the environment. The Plasma Wraith is pretty terrifying too. Completing the first part of the final boss in one day was actually pretty challenging. I know there are ways to glitch it though to make it easier.