Magnificent Duelist

You hone your skills as a one-on-one combatant, spending many hours gaining an intimate understanding of the art of dueling and learning the rigid code of honor needed to properly wield it. You demand a fair fight, using your phenomenal skill to dominate opponents. Many nobles use this archetype to prove their perceived superiority to others, and many independent mercenaries and knights are part of it as well. 

Glorious Challenge

Starting at 3rd level, you become a skilled duelist. You can use your bonus action to force a creature within your reach to make a saving throw. On a failure, the creature has disadvantage on attack rolls targeting anyone other than you and you no longer to need advantage to sneak attack them, so long as you don't have disadvantage on the roll, until the start of your next turn . This effect ends if you damage another creature. The DC for this ability is equal to 8+ Charisma Modifier+Your Proficiency Bonus.  

Tools of Combat

Starting at 3rd level, you master the necessary tools to hold your own in one-on-one combat. You have proficiency in shields and medium armor.

Indomitable Warrior

Starting at 9th level, you become a skilled defender, capable of enduring any attack. When you fail a saving throw, you can reroll the saving throw and take the second result. You can only do so once before needing a short rest to do so again. 

Lunging Strike

By 13th level, your great skill in combat allows you to pursue fleeing creatures. When you hit a creature with an opportunity attack, you can move up to half your movement speed as part of the same reaction. This movement doesn't provoke opportunity attacks. Moreover, your reach increases by 5ft.

Grandmaster

When you reach 17th level, you achieve the title of Grandmaster duelist,  declaring you as one of the most skilled warriors in all the realms. When a creature within your reach misses an attack roll against you, you can use a reaction to make an opportunity attack on the creature.