Greg Pak began as a New York filmmaker with a reputation for strong Asian-American themes, but he was picked up as a writer for Marvel Comics in 2004 for the Warlock limited series. This led to several other limited writing assignments from Marvel in 2005, including X-Men: Phoenix - Endsong, Marvel Nemesis: the Imperfects, Iron Man: House of M and Marvel 1602: New World. In an issue of Amazing Fantasy, he created a new Marvel character that he would become known for, Amadeus Cho.
Pak's major rise in popularity came when he wrote the Planet Hulk epic in the Incredible Hulk series. This story was so well received it led to him helming his own small Marvel event, World War Hulk. It was in this early part of his Hulk run that he created the characters of the Warbound, brought Amadeus Cho into the spotlight and introduced Skaar, Son of the Hulk. Pak developed the Warbound and Skaar further in their own respective limited series and ongoing series and eventually returned as the writer of Incredible Hulk, which was temporarily renamed Incredible Hulks to reflect the larger cast of characters Pak had included.
Pak, teaming with fellow writer Fred Van Lente, launched Incredible Hercules immediately after World War Hulk as a buddy book starring Hercules and Amadeus Cho. The series proved to be a surprise success both in critical acclaim and sales. This allowed Pak and Van Lente to write the complete Incredible Hercules saga they had in mind, concluding with the small Chaos War event. When that ended, the writing duo launched the Herc series, presenting a more grounded take on Hercules without the presence of Amadeus Cho.
With his run on the Hulk nearing its end, Pak teamed up again with Van Lente to launch Alpha Flight, having resurrected the dead team in the pages of Chaos War.
Pak has recently began work for DC comics. He is the current writer for Batman/Superman. He has also done Villain's Month issues for Doomsday, Zod and Darkseid. Pak has also recently taken over the writing duties of Action Comics, starting with issue #25.