General Matthew Shrieve is a corrupt general of the U.S. Army.
After Oliver Queen stopped Chien Na Wei from selling the Omega, General Shrieve told Oliver he had to return to China for a debrief, in return, he would allow Oliver to go wherever he wished. Upon finalizing Oliver's debrief, Shrieve kept his word and allowed Oliver to go anywhere he wished, but he had to go to Japan with the Yamashiro's first. It turns out, while Oliver is infiltrating an A.R.G.U.S. field house, General Shreve had held Amanda Waller prisoner. He thought that Hong Kong was a military threat and was planning on using the Omega to destroy the city.
Matthew was shown at first to be a man of honor, letting Oliver and the Yamashiro's go once their business was done. Matthew also at first shown to have good morals as he removed Amanda Waller's authority as the leader of A.R.G.U.S. for committing unspeakable acts. But he later revealed himself as a manipulative liar, sending men to kill Oliver and Maseo's family. He also held Amanda hostage and likely tortured her. He is probably as sociopathic and immoral as she is, if not worse, in his pursuit of his goal to wipe out China that he believes to be a major military threat using the Alpha/Omega viruses that would kill thousands of innocent people.