Sarasaland Adventure v4.0 (SMBX) - Snowflake Substratum (5-5; both exits)
Info: https://rpgmaker.net/games/4216/
The second half of World 5 has you climbing Chai Icecap's big mountain, and this level starts at the base of said big mountain. It is also pretty tricky overall; some parts, you need to use the Ice Flower to freeze enemies and then use them as platforms to proceed and others encourage you to use frozen enemies as weapons. Of course, freezing enemies to make platforms isn't a MUST; if you can use Peach's hovering technique well enough and bounce off a few of the paratroopas, you don't need to do any freezing at all. I show that it's entirely possible to navigate those sections when I run the level again to get the secret exit. Speaking of the secret exit, isn't too hard to get to as long as you can reach the green ? block. I also like how the stage starts with the snow falling lightly, and gets heavier as you get further - it really comes down in the last area; visibility can be poor there, so take your time going through there.