To me, I really don't have one since I haven't went around within this wiki much for a long time, and also I haven't looked into the "Main 9" much. So the best I'll choose is Level Alien World. Although popular, it is kinda underrated said by a fandom user here a while back.
So yeah, what backrooms level do you think is underrated, answer and discuss :)
Also, here's a sketch art piece of a created abomination in which was once a dog. This sketch may end up within the Unfinished page "S E N T I E N T" to add a documentation about this entity, and also expand some interesting things about the page, since the page is currently on halt so that I could create lore, and ideas.
Enjoy :)