You want people to love your protagonist. You want people to root for him or her and be on their side. You want them to believe that the person they like might be able to win this fight.
But you don't want people to think they can win too easily.
An unworthy opponent is an opponent not worth writing about.
If you're going to take the time to invent a villain, make it someone that people can't forget. Make it someone who scares your readers. Make it someone who gives your protagonist a run for their money.
You don't want readers to root for your antagonist more than your hero, but you still need them to believe the villain is worth their time. Make your villain worthy of your story.