Amadeus Cho, also known as Mastermind Excello, is a fictional superhero appearing in comic books published by Marvel Comics. Created by writer Greg Pak and artist Takeshi Miyazawa, the character first appeared in Amazing Fantasy vol. 2 #15 (January 2006). He usually appears as a supporting character or sidekick in books featuring The Avengers, or individual members of that group, such as Hulk or Hercules.