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

Well, it depends on who you ask. In general, the five heroes were designed so that any faction can win against any other, as long as they develop properly. I agree with those who say that. And in theory, even Haven can defeat Inferno. The main thing is to avoid having Nightmares and Cerberuses go first, and instead use Paladins, with Axel's Guardian being the best. I remember him defeating Marbas in a duel on 3.0. Paladins don't suffer losses; we can resurrect them with Archangels. Also, don't forget about the spells Holy Word and Unholy Word. Max out Holy Word for all light factions. So, even a professional player using Inferno against a professional player using Haven can lose. Inferno excels in offense, while Haven excels in defense. So, let's give them a solid defense and a skillful counterattack ability.