Dminator is a very old modified Doom E1 intended for co-op. It has lots of extra monsters and vast quantities of health and ammunition. In particular, pickups especially spheres are in double, triple, or even quadruple so every player can have one.
The monsters are numerous and it can be considered an early form of slaughter map, but it is not that difficult. Although, it helps a lot if you play one map after the other and carry your weapons forward - some maps have really nasty openings if you only have a pistol, I think.
There is a lot of backtracking and switch-hunting. You will need to have a good working knowledge of the original IWAD episode, as now pretty much every place that used to be a secret area has to be visited, as well as a lot of places that before were simply inaccessible. The routes can be inscrutable and I found myself resorting to a map editor at several points. I think at least some of the time the author is expecting the player to die and respawn at the start, as that is often the fastest way back to whatever door the button you just pressed opened. Unfortunately not a method available in single player...