The Hell map. Not in terms of difficulty, but in terms of how tedious it is to play. It's not a strategy game; it's just one long, monotonous quest. Everything boils down to finding a hidden passage, artifact, or event. There's nothing else interesting about this map. The battles, especially after obtaining the vulnerability medal, are nothing but a bore.
P.S. Regarding the game freezing, starting at a certain point. This is not a bug of the map itself, but of the heroes. On practically any map where there are large armies and the game lasts for more than 10-15 months, you can encounter this. Without going into the reasons, I found a solution. Using a debugger, it's easy to see that the program enters an infinite loop in two places when the game freezes. If you "nop" the conditional jumps that are used to exit the loop at that moment, the game will continue to run without any visible problems. In any case, I haven't noticed any deviations in the gameplay. You can, of course, patch the executable file on the disk in advance, but I prefer to patch only the memory when the game freezes.