JJWay's list "SuperHero/SuperVillian Names" of 3 great name ideas: Piotr - Thanos!

SuperHero/SuperVillian Names

With the increased popularity of Superheroes right now, I have put to together a list of the real names of Superheroes-and Villians. Because of the vast amount of Heroes I am only doing Heroes used in movies, otherwise the list would never end!

A variant transcription of Russian Pyotr, and also the Polish and Belarusian form of Peter, classic and still very popular there. 

Piotr

St. JOhn is mainly (but rarely) used by Catholics in England -- there's one in Jane Eyre.  This would probably be too cumbersome for most American kids. 

St john

Thanos originated as a short form of Athanasios, a Greek name meaning "immortal." It is composed of the elements a, a negative Greek prefix, and thanatos, meaning "death." St. Athanasius, who used the Latin spelling of the name, was a bishop of Alexandria and known for his opposition to Arianism.
 
Though this is a perfectly respectable Greek choice, be aware that Thanos the Mad Titan is a sinister Marvel Comics villain.