None of the Bullet Bills at the beginning and in the following parts were very threatening, and there was one part with a bunch of haphazardly placed Hammer Bros. You can only have one at a time per screen or else the sprite tile doesn't appear, unless you use SA-1.
I got the feeling that things were being haphazardly placed rather than arranged in a meaningful, strategic way to deliberately hinder progress. The general aesthetics were lacking (cut-off pipes and 2x2 floating Munchers strewn about) and the end killed me.
--------------------Legacy custom music
How am I so creative? I think taking walks might have something to do with it.
Every single level I will ever make in SMM2 will be easier than Ultra Necrozma.