Destr0yer

The skill set is mixed, so you need some luck when you first enter the 20s. It'll be easy to clear once you hit around AD1.

If you can't mash, your feet have to be fast...

The half-beat run in the middle is indeed difficult if you play it with precise taps, but it's very easy to bracket-step at a level 20 standard. As for the late spike, the short trills and holds in the middle of the run slow down the tempo, so I don't think there's a section that kills you in one go.

The repeated half-steps in the middle and the late spike are definitely level 20.