In recent history, i finished an entire campaign of Brutal Doom: Project Brutality on its hardest difficulty settings (last man on earth skill level + death wish monster spawns) on a map pack called Maps of Chaos. This was a very difficult and nearly suicidal task considering that the hardest skill level greatly increases the enemy's damage, reaction time, and their health while enabling death wish monster spawns meant that i had to fight the strongest enemy variants from the first map till the end since the monster spawns are fixed to only provide these enemies and nothing less. This meant having to fight against the extremely powerful monster variants such ad heavy machine gunners, belphegor barons, overlords, rocket launcher wielding infantry men, auto shotgun guys, flesh wizards, and annihilator cyber demons from level 1 to the end: all while these enemies literally come from the very depths of hell and beyond.
To put that in perspective, imagine having to play the first few maps/hours of fallout 4 but at the start of the game you have to fight the strongest monster variants such as mythic deathclaws, ancient behemoths, gunner lieutenants, enraged fog crawlers, albino rad scorptions which are mob variants that should only appear when you are at a high enough level and play time.
(But thats a mod not a commercial ga... mods are full games too! Now if someone makes a fallout 4 mod with the idea i had in mind then that would make for a very fun and nearly suicidal experience)
As for a rather difficult but surely beatable game i havent bothered finishing yet, Wolfenstein: the new order on Ubermench difficulty. .__. The game on this difficulty setting is pretty unfun when every enemy takes almost an eternity to kill off which means you gotta be really good at your headshots. The very high damage the enemies can do on uber is very manageable but the unforgivingly beefiness of every mob, especially those nazis on heavy armor makes the game a little too stressful for a casual playthrough.
