Nobody told me Super Mario Maker was gonna get this real, god damn.
While there are plenty of batshit difficult courses circulating in Mario Maker, my favourite type of level is the kind that tries to tell a story. The tools are pretty limited, at least when it comes to narrative design, so people have to get really creative -- which in turn, often produces really great stuff.
The course above, for example, was sent to me by Theorymon (its creator), and it tells the story of a Lakitu friend that Mario makes while adventuring. Eventually, the course presents you with a difficult choice related to that friend. I went with the more renegade option here, and got a pretty depressing ending. You might choose otherwise: you can try the course out at: 86AD-0000-0067-F2EF.
That boo at the end though. My heart!