- Killing everyone. The enemy has an evil army and is killing everyone for world domination. But what happens when he wins? They are just killing everyone and taking no slaves, so who will be left to do everything? Will he make his evil goblin bake him cake? Will another one spend his days nurturing a crop of watermelons? Or will he sulk because he clearly didn’t think this plan through?
- Evil Creatures. An easy way to make an enemy is to say they are all evil creatures. Now, I love Lord of the Rings as much as the next nerd, but it gets a little old to believe that “oh, they follow him because they are all evil,” and that is that. You can have a war-hungry enemy, but it would make it seem more real if you give the army a reason to be war-hungry. Are they promised better farmland? Will they get power? Riches? What’s motivating them to listen to the king? Why do they care if they win?
- The faceless army. Too often writers only concern themselves with the heroes of stories and that makes an entire army of boring look-a-likes and the evil leader who we don’t meet until three books later. Give some of your enemies a name; show us that his army is as passionate as he is.
- No clear plan. They are supposed to be a smart enemy, but show us that! Show us them damming up the river upstream to stop water from getting to the good guys. Show us them spying, scouting, and giving false information. There can be more to an enemy army than facing off on in a field.