Pure run guide is beyond outdated and is getting harder and harder to manage since the dev generally nerfs things to balance corruption, while not accounting for pure. The main roadblock used to just be Belphegor due to lacking magical defense, but almost everything else was reasonably achievable until the lava dungeon started developing deeper and you needed the academy. At this point, pure is nothing but a ng+ pipe dream.
1. Starting Holy Water prices make money early on disgustingly impossible to manage without simply forgoing day 1 purchases which will bite you later since you'll need them eventually anyway.
2. Slime has been repeatedly nerfed. It's becoming increasingly unusable, especially given the 100 day time allotment, and is mostly a meat shield outside of the wind slime's benefits.
3. Materials have been nerfed further weakening one of the only ways pure can empower themselves - corruption plays get incredulous bonuses through passives that pure just cannot keep up with. It makes sense for corruption to be easier, but it doesn't feel like pure is controlled difficulty that yielding to corruption makes more difficult, it feels like it borders on to impossible.