I took a deeper look into all of the things that do and don't affect RNG and was able to make a level that simply requires you to enter a precise code to win!
Now I would do the Konami code as its well known, but left and right inputs need to be frame perfect to work and I think grinding frame perfect input press and release timings is not a good way to showcase this.
The code I will be using for this level is Up, B, A, Down, Down, B, A, Up, Down, Up, B, A
This is a simple code string that's in the level, the description for the level and requires you to press this and ONLY this in the subworld to survive. The RNG seed has 5 very specific RNG checks (almost Lucky Draw levels of RNG) which make this very difficult to brute force.
Level Code: J9J-QL1-RDF