The Brave and the Bold #1

Marcus, a young shepherd, is grabbed and falsely accused of attacking a Praetor by the conniving soldier Cinna. Sentenced to a slave galley for life, Marcus becomes a muscled giant. He saves the crew from a loose lion by slinging his chain. He's sold to Cinna and handed to the gladiators and trained. He beats down hated rivals and rides a bull, despite sabotaged weapons from Cinna. He even wins the chariot race with only a shield. He's given the golden helmet and breastplate of the Golden Gladiator - but Cinna plots revenge.