Character Analysis
Éomer seems like a good guy. He doesn't like Wormtongue creeping on his sister and poisoning his uncle, and he lets him know it. He takes his Rohirrim and kills a whole company of orcs. And at the end of the day he returns to his people with Gandalf and rides down into the valley, slaughtering Saruman's hordes and turning the tides of the battle. Good job, Éomer.
But what about the whole middle of the movie? Where is Éomer then? Éomer tries to help Théoden, but upon his exile he takes the armies of Rohan and rides around killing orcs. We already established killing orcs is a good thing, but we're thinking Théoden could've used those horsemen when traveling to Helm's Deep. Maybe he would have even been able to defend Edoras, and there surely would have been fewer lives lost at Helm's Deep.
Maybe Éomer didn't have a choice and was just helping from a distance as best he could. But another way to look at it is that he abandoned his people in their greatest time of need. While he gets a wonderfully heroic ending, we're wondering if he's a hero or if his charge is his act of redemption for leaving his people defenseless.