Oh, yes. I've been writing my super hero novel since 2009. The main character is a girl with gravity powers. I gave her the super hero name Singularity.
Earlier this year, I discovered Marvel™ are introducing an all-female Avengers™ comic, including a new super hero character called...Singularity.
Oh, and they also had a super villain called Singularity (he's dead now, or as dead as you get in comic books) since 2010.
Now, you might have spotted the timing. I was a year ahead of Marvel™, and I might even be able to prove it. But...that means taking on the evil empire that is the Marvel™/Disney™/Pixar™/Star Wars™ legal department. They probably have an annual budget larger than that of most nations. Enough money to keep me in legal proceedings for the rest of my unnatural life.
Plus, using a name in a Work In Progress, and Publishing a Trademarked™ Character™ Name™ are probably two very different things. Marvel™ can also argue their heroes and villains are household names, while no one's ever heard of my characters, because they are as-yet unpublished.
So I've had to change her super hero name.
And a few months later, I discover a Japanese anime is about to introduce a new super villain...with the same name I've been using for my first super villain. And it's not even a Japanese name! AAAAAAAAAAAAARRRGGHH!!!
P.S. The word superhero™ (as one word instead of two) is owned by Marvel™ and DC™ comics.