Sentry was suppose to be Marvel’s version of Superman. He had every ability you could ask for: flight, invulnerability, telekinesis, the power of “a million exploding suns”. He also had a an alter ego, and was his own worse enemy.
While he was in high school, Robert was accidentally empowered by a serum created by a man called The Professor, giving him superpowers. After he beat up a bully, Robert went home, created a costume, and became Sentry, The Golden Guardian of Good. He was accompanied by CLOC, an organic computing system that uses mathematics and logistics to help Sentry strategically deal with disasters that are threatening the Earth. He was definitely one of Earth’s mightiest champions.
Sentry’s weakness was his other forms: he was actually three entities sharing one body. Robert, Sentry, and Sentry’s nemesis, The Void, who believed he was the most powerful of the three. Whenever Sentry would use his power he would become obsessed from it, almost becoming addicted to it. But the more power he uses the more The Void would manifest, and become more powerful.
During the events leading up to the Siege storyline, The Void confronted Robert’s wife Lindy. She felt threaten, and picked up a gun and shot him in the face. After Sentry came and confronted The Void, Sentry flew to the sun telling The Void that he was going to end them for her safety. Lindy begins to have a conversation with CLOC and reveals Sentry’s true origin. She reveals that Robert’s transformation was due to his drug addiction at an early age, and he and a friend broke into a lab to steal equipment and any drugs they could so they could manufacture methamphetamines. Robert, not knowing what it was, saw the opportunity to test some of a formula that was cooking and decided to take it because he needed a fix. Instead, Sentry was born, and with the help of Reed Richards, he was able to cure one addiction, but because of his addiction to the power he became addicted to himself.
Norman Osborn devised a plan to take control of Sentry. He ordered Bullseye, now posing as Osborn’s version of Hawkeye, to kill Robert’s wife Lindy. Osborn staged an attack on Avengers Tower and had the building evacuated. Hawkeye took Lindy off in a helicopter and killed her over the ocean.
After the “attack” was taken care of, everyone came back except Lindy, which sends Sentry into a panic. Hawkeye tells him that Lindy told him that she couldn’t handle being his wife anymore because she was afraid of him, and jumped out of the helicopter and committed suicide. This sent Sentry on a rage, but allowed Osborn to manipulate him into controlling him.
After the “attack” was taken care of, everyone came back exept Lindy, which sends Sentry into a panic. Hawkeye tells him that Lindy told him that she couldn’t handle being his wife anymore because she was afraid of him, and jumped out of the helicopter and commited suicide. This sent Sentry on a rage, but allowed Osborn to manipulate him into controlling him.
In the Siege storyline, Osborn hatched a plan with Loki to take down Asgard. During the battle, Osborn unleashed Sentry on the city and he tore right through it. Aries realized this was all Osborn’s doing, decided to attack Osborn. He had warned him before that if Osborn had planned this he would take his head off. Osborn tells Sentry to attack Aries. Not only does he defeat the god of War, but he rips him in half on live television.
This battle was eventually won by the Avengers and resulted in Robert Reynolds asking for them to kill him. Thor struck him with lightning, wrapped up the remains in his cape, and floated him into the sun, and he was gone.
It was really a sad way for Sentry to go, but because he has regenerated after seemingly being dead before, comic readers believed he would have resurfaced by now. Even if Marvel decides to keep Robert Reynolds dead, they should consider bringing Sentry back.