I think the most difficult campaign for the Elves is "Lord of Vampires."
Someone says that the campaign for Relag is difficult, especially mission 3. I say there's nothing difficult here; I just went through it and tore them apart like a dog tears through a felt boot. The only thing that was a little difficult was when I first started playing and couldn't find the sawmill and the mine (I couldn't build anything). But once I found them, I passed it without any problems.

And it's also difficult to fight Gilren. But otherwise, everything is easy, and the campaign for Humans is like a walk in the park. I'm playing on difficulty level 1.0. If you have any questions, feel free to ask.