To casual viewers of the Marvel Cinematic Universe, Ronan the Accuser is little more than "that angry blue alien with the powerful mallet." But Marvel Comics fans know there's a lot more to the infamous enforcer of Kree law. Ronan has a rich comics history that stretches back to the late '60s, and he is named among the best Avengers villains. He's one of the most significant members of the Kree, a humanoid, blue-skinned race that originates from the planet Hala. With their fondness for conflict and technological innovation, the Kree are basically Marvel's Space Romans.
Ronan is also a member of the Kree Public Accuser Corps, a heavily militarized police force. As the Supreme Accuser, Ronan is effectively the Attorney General of the entire Empire, answering only to the Imperial Minister and the Supreme Intelligence - the bodiless, all-knowing being that governs the Kree. As referenced in Captain Marvel, Ronan is a long-time antagonist of Captain Mar-Vell - Carol Danvers' male precursor in the comics. But his undying devotion to his people has also put him in the crosshairs of the Fantastic Four, the Guardians of the Galaxy, the Inhumans' Black Bolt, and even the Supreme Intelligence itself, making him one of the most notable Marvel villains ever written into being.
He Has A Messy Relationship With His Extended Inhuman Family
The Kree and their experimental progeny, the Inhumans, have a complicated interspecies relationship. Ronan has exchanged many blows with Black Bolt, who, at one point, usurps him as Kree Emperor only to then welcome him into his extended family when Ronan is wedded to Crystal, the sister of Black Bolt's wife, Medusa.
Having grown very fond of each other, neither Crystal nor Ronan are thrilled when Black Bolt disrupts their union after agreeing to a truce with the Supreme Intelligence. This causes more friction between Ronan and the Inhuman royal family.
He Briefly Gained Ego The Living Planet's Powers
We glimpse what Ronan can do with an Infinity Stone when he wipes out the Nova Corps in one fail swoop during MCU's Guardians of the Galaxy. He grows even stronger, however, during the Maximum Security storyline when he is forced to guard a newly established intergalactic prison on Earth which holds Ego the Living Planet.
After Ego becomes one of the facility's first prisoners, Ronan manages to act as a conduit for the cosmic being's godlike powers. Predictably, Ego plans to take advantage of his incarceration and take over Earth using Ronan. Luckily, Quasar - the cosmically appointed protector of the universe - manages to absorb Ego into his own body before zooming off into deep space, leaving Ronan defeated.
He Served As Kree Emperor (By Popular Demand)
Proving that he's not such a bad guy, after all, Ronan allies himself with Nova and his most adverse Skrull nemesis, the Super-Skrull, in the fight against the highly destructive Annihilation Wave during Marvel Comics' Annihilation event. Despite being wrongly stripped of his Supreme Accuser rank by the House of Fiyero guild, Ronan's reputation means he also still has enough Kree allies willing to follow him into a fight.
Ronan ousts the traitorous guild, who are planning to align themselves with the Wave, and is forced to terminate the Supreme Intelligence, which has become incompetent. In the aftermath, he emerges as the clear candidate to repair the fractured Empire and is welcomed as the savior of his people.
He Became Self-Destructive After His Planet Was Wiped Out
Ronan is sent into a downward spiral after his beloved homeworld, Hala, becomes a casualty during the destructive events of the Black Vortex story - a Guardians of the Galaxy and X-Men crossover from 2015. The mourning Accuser us left to try and rebuild his fallen empire from the ashes left behind, swearing to honor all who have perished in the conflict.
He is eventually discovered by his estranged Inhuman wife, Crystal, and decides to take out his grief on her crew. Crystal attempts to console him after he confesses he blames himself for Hala's fall and that the end of their marriage made him emotionally weak and volatile. Ronan even tries to take his own life as penance, but Crystal manages to stop him, and with the help of Marvel Boy, they find a way to revive the Supreme Intelligence and give Ronan a renewed purpose.