Would this be too much for readers?
Question: What do you think of a fantasy war story that is written from two main character's perspectives? One pov would be from the side of a single man fighting for his country while the other pov would be from the "Warleader" of the other country. Do you think it could work with them in a sense being each other's antagonist?
A lot of writing help articles say not to go with the antagonist's pov but if I am able write this the way it feels to me I think it would make for a better story. Both of my characters I have in mind have plenty of flaws and they are each other's opposite. Answer:
You can certainly write from more than one perspective. The result would be a novel that contains more than one story (since every POV character is the hero of his own story).
The challenge here is that writing from the Warlord's POV will tend to develop the reader's empathy for that character. In a simple genre tale, villains are generally portrayed as evil sociopaths/psychopaths and not people the readers should empathize with. That's why villains are often made into monsters.
However, if you were trying to present the notion that both your hero and your villain are characters caught in situations not of their choosing, or influenced by forces outside their control it could work. You could have a story where the two come eventually together and realize neither is the real antagonist.
Or you might use the technique as a vehicle for a philosophical argument. For instance, political opinions have often wavered between whether great conquerors should be seen as tyrants or heroes. (It rather depends on whether your family gets wealthy or killed because of the conquest.)
The bottom line is: there's no rule against what you propose, but you need to know why you are doing it and what message you are trying to send.