I'm just gonna show you the hardest level in MY OPINION.
Easy: Marred Dreams - It was between this and PV, but this was just slightly harder. The main reason is that PV has a insane cut for regular severs, allowing the sever to finish fast if their not lazy. Marred Dreams is fasted paced and only has acid, making it harder.
Normal: Forgotten Tombs - Once again, this was between two maps, being sky sanctuary and forgotten tombs. Forgotten gives you more time with harder jumps, and sky gives you less time with easier jumps. And, on both of them one mistake is pretty much dead. However, it is possible to JUST make it out alive on sky if you fall, which can't be said for forgotten, which only has lava.
Hard: Sunken Citadel - What do you know, the new map is the hardest. This map is fast paced, and no mistakes can be made, especially when you do it solo. This wasn't a very hard choice, but sedimentary temple is 2nd, and wild Savannah is 3rd.
Insane: Dark Sci Facility: This one shouldn't be a big surprise, but beneath was very close to taking this crown. Dark sci Facility is fast paced, despite having a shortcut that is very useful on regular servers, its useless when playing alone. The buttons are hard, the lava rises fast, and jumps are hard, making this the hardest insane map