People claim presenting the "best puzzle of all time" all the time here but if any puzzle deserves that title, it is this one. Before the idea was accomplished, most problemists believed it was impossible and that includes me. Magnificent!
Best Chess Puzzle of All Time

This is an absolute masterpiece and it's so mind boggling to understand why each promotion is necessary for the mate-in-4, I'm amazed by the person who composed this immortal study!

I mean, I get that the promotion parts were interesting, but this type of position could never occur in a real game, and like he said in the video, although the shortest checkmate is mate-in-4, there are many ways to checkmate in 5 moves.

I mean, I get that the promotion parts were interesting, but this type of position could never occur in a real game, and like he said in the video, although the shortest checkmate is mate-in-4, there are many ways to checkmate in 5 moves.
it's supposed to be a composition, it's supposed to be outlandish
The Babson Task is my favorite chess puzzle of all time. It's white to move and mate in 4.
I made a video that explains the puzzle and discusses the fascinating history of the problem. I thought some people here might enjoy it!
(If you haven’t heard of the Babson task, you’re really missing out)