The main antagonist, Lucifer is a Hunter, psychic beings sent to destroy anyone unjust in the world. Of the three Hunters, Lucifer is the most powerful and the most fanatical, causing a mass pile-up just to catch Tachihara and killing anyone who attempts to aide the Red May terrorists, the Special Service agents included. She is finally killed when Raiden's suit detonates in front of her. In the manga, she is killed by a cybernetic Angel. (Source: Wikipedia)
Maisaka is a powerful figure in Japan; he is in command of all the police forces. He is responsible for awakening the hunters and attempted to wipe out the Special Security Force. He was killed when a tape recorder inside his helicopter detonated. (Source: Wikipedia, edited)
A hunter with the appearance of a young girl. She possesses pyrokinetic powers. Asura and Freya appear to be very close. She is killed by Lucifer in the anime and Angel in the manga. (Source: Wikipedia)
The only other female Special Security agent, Peace handles explosives and is generally paired with Hacker. It is later revealed that she is in love with him. Peace dies when Lucifer drains her mind in the anime. As with Hacker, she is killed by Freya in the manga. (Source: Wikipedia)
The new head of the Red May, Tachihara initially manages to escape from the Special Security Force but is eventually captured and tortured. Hacker and Peace attempt to bring him to Ichihara's laboratory for safety, but the three are killed by Lucifer on the highway. (Source: Wikipedia)
One of the Special Security agents. As his name implies, he handles hacking duties, but also participates in firefights. He is killed when Lucifer takes control of his body and causes him to detonate a grenade in the anime. In the manga, he is killed by Freya. (Source: Wikipedia)