Comments from the Finger: This is another of those entries into what I consider Iconic archetypes. Nothing mind-boggling, but a good direction to send someone who's new to D&D, but wants something a little different for their character.
The violent showmen of bloodsport, and the avatars of slaughter, archetypal gladiators revel in battle. More than that, they transform killing into performance art. The crucible of fighting pits and coliseums produce gladiators in droves, but only the most merciless and popular survive to make their reputation and escape as free men. As such, free gladiators often have as much celebrity as they do a genuine love of brutality.
Appeal to Audience
At 3rd level, if there is a non-combative audience watching you fight, once per turn, you can gain a bonus to a melee attack roll equal to the number of people in the audience, up to a maximum of your Charisma modifier.
At 3rd level, even if you fight with little armor, your panache in combat makes you challenging to hit. While unarmored, your Armor Class equals 10 + your Dexterity modifier + your Charisma modifier.
By 7th level, your reputation as a deadly combatant precedes you. You have advantage on Charisma (Intimidation) checks against humanoid creatures that have heard of your fighting prowess.
At 10th level as a bonus action, you can enter a special fighting stance. Until the beginning of your next turn, each time a creature within your reach attacks you, it has advantage on its attack roll, but provokes an Opportunity Attack from you when it hits you, which you can make without expending a reaction.
By 15th level, when you hit with a melee attack, you can add your Charisma modifier to your damage roll.
At 18th level, when you hit with a melee attack, you can deal maximum damage in addition to the damage roll. This attack ignores damage resistance. After using this ability, you must complete a short or long rest before using it again.
Most successful gladiators perform in the coliseum with some kind of theme to boost crowd appeal. For example, you might wear furs to look like a werewolf, or you may fight with a showy but impractical exotic weapon. Whatever gimmick you choose, it's a vitally important part of your gladiatorial persona and should be reflected in your Personality Traits.