Every good book has a villain, antagonist, something that is working against the main character. It can be a person, a monster, the weather, pretty much anything that stands in their way.
One of the keys to a great story is the level of skill that something exhibits. They must be very difficult to beat, but not impossible.
Like in Angry Birds. If no matter where you pointed the birds the pigs were destroyed, how long would you keep playing? Would you mindlessly keep swiping the screen, beating level after level easy peasy? I’d probably be bored after the second level. (Okay maybe it’d take me five levels—watching those birds fly is pretty entertaining).
Too easy is no fun.
On the flip-side, what if a level was so difficult it was nearly impossible? Yeah, there are some tricky levels, but I’m talking, precise angles and the bird must land in the exact spot. The-don’t-succeed-the-first-fifty-times hard. How long would you keep trying without getting frustrated?
The same goes for your villain. If the main character wins with no sweat, then things are too easy. If the villain is an absolute power and cannot be defeated ever, it will frustrate the reader.
How do you get around this?
First, include at least three try-fail cycles. If the reader sees the main character thwarted in their efforts, they know that the villain isn’t super easy to defeat. (Note: the at least three try-fail cycles does not apply to Angry Birds)
Second, give your hero small victories. Do this even if their victories turn out to not be so victories. (Example: Have the hero succeed in stealing the map from your villain, but it turns out to be blank). This will instill in the reader a hope that everything will turn out okay. It gives them a reason to keep cheering your hero on.
What do you think is a good balance of strength for a villain?