Thaddeus E. "Thunderbolt" Ross is a former Lieutenant General of the United States Army. During his career, he was put in charge of the military project called the Bio-Tech Force Enhancement Project, aiming to recreate the Super Soldier Serum. However, the experiment led to an accident which transformed the scientist Bruce Banner into Hulk. After a long hunt, Banner was captured, only for Ross' subordinate officer Emil Blonsky to transform into the monstrous Abomination which forced Ross to accept Hulk as an ally and allow him to escape after the battle in Harlem. Ross would never hunt down Banner for the years to come.
Five years after that incident, Ross left the Army and started serving as the United States Secretary of State. During this time, Ross approved the Sokovia Accords, which aimed to control the actions of the Avengers. When Captain America publicly disowned the accords and went on the run with the Winter Soldier, Ross ordered Iron Man to bring Captain America into custody. Ross arrested many of the Avengers and locked them up in the Raft, but when Captain America learned that Helmut Zemo was to blame for the devastation, he freed the prisoners, much to Ross' fury who tried contacting Stark only to be put on hold by the latter, angering him even more.
Ross later struck a deal with Scott Lang and Clint Barton, placing the heroes under house arrest. Learning of the Vision's absence from the New Avengers Facility, Ross contacted James Rhodes, discovering that Captain America and the fugitive Avengers have returned, promptly ordering Rhodes to arrest Rogers, who ended the call, earning Rhodes a court martial and Ross's fury.
He was the fifth tritagonist of The Scar Chronicles. He was voiced by John Vernon.