If your hero is up against a villain, better make sure that villain’s powerful. Sure, you need conflict to make a story. Or should I say, an interesting story. But the writer of a post iI just read used Voldemort and Sauron as her two examples of good villains.
Characterisation is at the heart of any really good story as far as I’m concerned. Real people dealing with real situations. Or sometimes (as in speculative fiction) not-real situations. That’s when creating believable characters becomes absolutely crucial. If your characters aren’t believable, your reader won’t relate to them.