6. Captain Marvel (Mar-Vell)
After being exposed to toxic nerve gas, Captain Marvel developed malignant cancer. He spent the last days of his life on Saturn’s moon, Titan, surrounded by friends and allies who came to visit him. Even an ambassador of the Skrull empire came and awarded Mar-Vell with the Skrull medal of valor, stating that Captain Marvel was considered to be the greatest single enemy the Skrull Empire had ever faced.
Following his death, Captain Marvel was granted a posthumous honorary membership in the Avengers, and a monument was erected in his memory on Titan.
Though it was once thought that Captain Marvel had come back from the past via a wrinkle in space-time created during the construction of the Negative Zone prison, it was later revealed that this was actually a Skrull sleeper agent who had been programmed to believe he was the real Captain Marvel. Apparently, the programming had so completely overtaken his original personality that he killed the Skrull agents who were sent to terminate him and then destroyed several Skrull ships, ending his own life in the process. Though the real Mar-Vell surely would have been proud to see his imposter give his life to defend Earth during the Skrulls’ Secret Invasion, he’s still never actually been brought back.
https://scans-daily.dreamwidth.org/2032569.html?thread=68453305 Via scans-daily.dreamwidth.org
5. Ant-Man (Eric O’Grady)
As Ant-Man, Eric O’Grady was probably one of the least likeable superheroes ever. He repeatedly used his shrinking powers for personal gain and even became a practicing villain for a brief period after stealing the Ant-Man suit. However, he eventually got the chance to redeem himself when Steve Rogers overlooked his past crimes and invited him to join the Secret Avengers — a team he was still a part of when he met his untimely end.
In a mission against the supervillain group known as the Descendants, O’Grady attempted to save a child and his mother. Unable to save the mother, he took the child and fled. But a group of android-like creations found them and demanded that Ant-Man hand over to the child. Even when his powers failed, O’Grady refused, choosing instead to single-handedly face down the Descendants so he could give the boy a chance to escape. He was killed in the battle.
For a time, it was thought that O’Grady survived to help Beast and Hawkeye escape, but that Ant-Man was later revealed to be a robotic decoy under the control of an evil scientist.
http://insidepulse.com/2012/02/23/secret-avengers-spoilers-which-avenger-falls/ Via IndiePulse.com