Complex sentence: Mandarin's Avengers (Avatars of the Mandarin) is a group of villains that work for their leader, Mandarin and belong to the Marvel Comics Universe and is most famous for their role in the "Iron Man" and "War Machine" comic series.
Split into simpler sentences: Mandarin's Avengers (Avatars of the Mandarin) is a fictional group of villains appearing in American comic books published by Marvel Comics. The characters work for their leader, Mandarin and are most famous for their role in the "Iron Man" and "War Machine" comic series.