Impactor Radia is a character from the television series Chōseishin GranSazer. He is a member of the Impactor aliens, a group sent to Earth as part of a larger plan concerning humanity and the giant warrior gods known as Chōseishin. Radia arrives on Earth alongside his companion, Lucia, and the two initially operate as a pair during their early missions.

In his human guise, Radia appears as a blonde-haired man dressed in silvery attire. This appearance belies his true nature as a fierce and hot-headed warrior. Radia is driven by pride and a strong desire to prove his own strength. He is contemptuous of the Gransazers, the human warriors who oppose him, and initially dismisses them as being too weak to pose a real threat in one-on-one combat. This arrogance is a defining aspect of his personality, leading him to take reckless actions that ultimately contribute to his downfall.

Radia's primary motivations are a combination of mission objectives and personal rivalries. He is determined to complete the tasks assigned to the Impactors, which include destroying the Chōseishin and the Gransazers. However, his judgment is heavily clouded by his personal feelings. He harbors romantic feelings for his comrade Lucia but is resentful of Logia, the enigmatic leader of their group, who also appears to be Lucia's partner. Radia feels a forced respect for Logia but is deeply jealous of his position and his relationship with Lucia. This jealousy fuels a desire to act independently and succeed where Logia might fail, in order to prove his own worth and superiority.

In the story, Radia serves as an initial major threat for the heroes, giving them their first real taste of the danger posed by the Impactor forces. His role in the narrative is primarily to be a powerful and aggressive antagonist whose actions force the Gransazers to discover new strengths. After a skirmish with the Gransazer Makoto Sorimachi, also known as Gorbion, Radia is forced to retreat and swears a personal vendetta against him. His key relationships are centered on his fellow Impactors. He is protective of Lucia, but his rivalry with Logia is a constant source of tension. He is also fixated on defeating Gorbion, seeing him as a worthy adversary after their first encounter.

Radia's development is brief but clear. Initially an overconfident fighter, he is humbled when his initial attacks are thwarted. When Lucia is wounded in battle, Radia decides to complete their mission alone, driven by a combination of concern for her and his own pride. This decision leads to a final confrontation with Gorbion and the Water Tribe Gransazers. Pushed to his limits, Radia uses his power to grow into a giant. However, rather than retreat when the situation turns against him, he refuses to back down, demonstrating that his pride has become his fatal weakness. He is ultimately destroyed by the Water Tribe's Chōseishin, Leviathan.

In terms of notable abilities, Radia is a capable hand-to-hand combatant. His primary weapon is a massive axe known as the Mega Axe, which he wields with great force in his armored combat form. As an Impactor, he possesses the ability to increase his size to gigantic proportions, becoming large enough to battle the Chōseishin in direct combat.