God-Tier Sniper's Interstellar Execution

"Heroes get statues. Survivors get to pull the fucking trigger." Ten years ago, Kaelen ‘Kael’ Cross was the Phantom Vanguard, the deadliest sniper on Earth who held the frontline during the Dimensional Merge. He didn't die a hero's death. Instead, his best friend and Guildmaster, Marcus Thorne, crippled his mana core, branded him a traitor, and kicked him into the Abyssal Rift, a subterranean hellscape where humanity dumps its worst nightmares. For a decade, Kael crawled through the dark, surviving on mutated flesh, pure hatred, and the muscle memory of a god. [Ding! The Interstellar Overseer Network has detected Anomaly-Class Malice.] [Would you like to broadcast your execution of this planet to the Cosmos?] Stripped of his magic, Kael accepts the contract. Armed with a rusted, scavenged heavy-crossbow, he steps into the spotlight of a trillion alien eyes. To Earth, he is a dead man. To the cosmic deities, bored dragon emperors, and abyssal monarchs, he is the greatest fucking show in the universe. Watch closely. He only needs one shot. — Description from novelcodex.org