Strength of Character
Your hero isn't the only one who needs to be tough. Your villain, too, must have strong goals, motivations, and resources. If he's a pushover with laughable henchmen, your reader's going to know without doubt that he'll be beaten, and what fun is that? (In romance, we know it anyway, but we like when you make us forget that and sit on the edges of our seats.)
Give your villain as much attention as you do your hero. Arm him with powerful resources and a darn good reason to hate the hero. The resulting power struggle is what makes epic battles epic. The more powerful your villain, the harder your hero must fight to win, and the more gripping your story will be. Remember that a hero shines best against opposition that offers him the greatest test of his heroic qualities. So save some of that super-strength for your bad guys!