Auto-translated
I can’t say for sure which unit combinations are best. Different ones are good in different situations. But in my opinion, the most powerful unit is the demon. It does have two drawbacks, though: it lowers morale and fights poorly in snow. The first drawback can be compensated for with a skill from the paladin branch. As for the second, you just have to accept it. But the advantages are numerous. Personally, I’ve used them as my main attack force ever since I first encountered them in Demonis, and I continued to do so until the end of the game. I even kept them for the final battle. They were heavily damaged there, but that allowed me to conserve my other troops. Overall, I think demons are almost like a cheat.