Against which factions is it easier for demons to fight, and against which is it more difficult?

imo, in terms of gameplay, the Dwarves are the most tactically versatile race. They can do a lot of different things. For example, you can separate one harpooner and, at a certain moment, pull a stack onto a cell so that the archers shoot with a direct shot. You can place two diagonally to pull troops together and hit them with fireballs, give the Jarls (or something like that) fire signs and hit them with Armageddon, push enemies back with bears onto fire walls, or push them away from your archers – there are many possibilities, plus runes, which provide a lot of room for developing tactical skills. But the first time I played with Dwarves, I didn't like them at all. And if you play as Ing, you'll probably know all the runes. Regarding the topic: It's difficult against a well-developed Wing from the Elves; they can kill everyone even without attacking once. Tactics and defense against them are essential. It's difficult against a skilled player using the Tower faction. It's easier against Orcs; it's desirable to have a Deleber to remove their companions. But if you don't have much experience playing with the Inferno faction, you'll lose to everyone.