Hardest DOS game you have played?

[VortiX]

Hardest beatable DOS game?

Without difficulty options:
Skyroads Xmas Special. This edition has tricky roads that make the pixel precise last road of the base game reasonable. I've returned to this one a few times throughout the years but it was only this summer when I spent my time on this game. Couldn't beat six of the roads (Meteor Storm 2 & 3, Mysterious Planet 1, Under The Ice 1 and The Eve 1 & 3). Almost every road requires tight movement and have supplies and traps hidden. It becomes a puzzle game in the latter half.

Honorable mention: Warcraft II: Beyond the Dark Portal

Max difficulty:
Final Doom. Haven't even tried this one but I can safely guess after playing through the previous Dooms on Nightmare! coop. a 64-map grind of bullet hell with respawning monsters makes this undoubtedly the hardest DOS game on the highest difficulty. I wonder if anyone has beaten Plutonia MAP22 on coop. There's a video of someone doing a UV+ with fast monsters.

Honorable mentions: Bio Menace, Ant Attack and Blood