Veteran Champion

Among the ranks of warriors stand those rare individuals considered elite. They possess exceptional talent and skill placing them above their peers. Among these elite warriors are the truly gifted—not simply the best in the kingdom, but the best in their generation. These men and women are known as Champions. The champion represents the pinnacle of the art of war, a titan of the profession, honed in skill at arms and blessed by preternatural strength and toughness. The archetypal Champion focuses on the development of raw physical power honed to deadly perfection. Those who model themselves on this archetype combine extreme rigorous training with physical excellence to deal devastating blows and stay at peak physical performance for as long as they can. After a long period of training in the art of the Champion, Veterans emerge showing that expertise and experience both go hand-in-hand when building the most elite combatants. Veteran Champions train themselves to an even higher echelon of physical prowess in multiple forms of combat giving them abilities in fighting styles they've learned.

(My idea of a "prestige class" version of the baseline standard Champion, for newer players that learn the game after choosing this class at the start.)

Superior Combatant: Improved Critical

Beginning when you choose this archetype at 3rd level, your weapon attacks score a critical hit on a roll of 19 or 20. At 13th Level you score a critical hit on a roll of 18 - 20.

Superlative Skill: Champion's Expertise

Also at 3rd level, your proficiency bonus is doubled for any ability check you make that uses Athletics or Acrobatics skill if you are proficient in that skill. At 17th level, you gain a passive strength check for Athletics that functions like Passive Perception where you take a 10 for a reactionary check instead of rolling.

Champion's Training: Remarkable Athlete

Starting at 7th level, you can add half your proficiency bonus (round up) to any Strength, Dexterity, or Constitution check you make that doesn't already use your proficiency bonus. Also, when you make a running long jump, the distance you can cover increases by a number of feet equal to your Strength modifier. At 15th level the long jump distance is increased by double your Strength Modifier.

Veteran Champion: Fighter Abilities

At 9th level, you choose another option from the fighting style feature and your combat experience drastically increases based on your two fighting styles giving you access to 2 special abilities. (Note: Uncheck the option under Fighting Style, this upgrade fully replaces it.)

Blademaster - Dueling Upgrade

Along with the normal Duelist fighting style option, Once per turn, if there is a successful melee attack against you, you can perform a parry and counterattack. This is a normal attack roll against the attacking enemy. A successful attack roll against the enemy will negate all damage from that attack. (Requires a sword, one-handed)

Duelmaster - Two-Weapon Fighting Upgrade

When you engage in two-weapon fighting, you can add your ability modifier to the damage of the second attack. Along with the normal Two-Weapon fighting you gain the ability to attack twice during a single attack. This attack gives the two attacks with +2 to damage but only those two attacks during that attack. This does not affect or apply to multiattacks, only one action can have the second option applied.

Greatfurvor - Great Weapon Upgrade

Along with the normal Great Weapon stance, as a reaction when you are dealt damage you can brace yourself against said damage. The next attack the player does deals bonus damage from the damage received (max 30). All damage dealt is whatever type the weapon does. On a critical hit, said damage is doubled. (Requires Great weapon, two-hands for ability use)

Heavy Brace - Thrown Weapon Upgrade

Along with the normal Thrown Weapon Fighting stance, if you haven't moved and are using this ability you can put the full weight of the weapon into the thrown weapons normal range. With this the weapon can push back the target 5ft + STR modifier. (Requires weapons with the thrown property)

Intervening Defense - Interception Upgrade

Along with the normal Inception ability, when a creature you can see hits a target, other than you, within 5 ft. of you with an attack, you can use your reaction to reduce the damage the target takes by 1d10 (to a minimum of 0 damage). If said damage is not fully negated you can choose to take the residual damage instead. (Requires a shield)

Offensive Shield - Unarmed Upgrade

Along with the normal Unarmed Fighting stance, your unarmed attacks are also d8 when using only a shield. And the shield itself counts as a weapon for unarmed attacks. (Requires a shield)

Shieldmaster - Defense Upgrade

Along with the normal Defense fighting style option ability, When you are hit by a ranged attack, you can use your reaction to deflect the missile. When you do so, the damage you take is reduced by 1d10 + your character level + your Constitution modifier. (Requires a shield)

Spot Mastery - Archery Upgrade

Along with the normal Archery fighting style option ability, You now have the ability to spot an enemy as a bonus action. Your next attack is given a +5 to hit but you lose of the ability modifier to the damage roll of the attack. If the attack connects at all (hitting the target's normal AC, regardless of a reaction like deflect missiles, parry, shield, e.t.c.) it will mark the target. All attacks made to that target are then, given advantage and the target is always tracked unless moved to a different plane or made to be invisible. This lasts until the next turn. (Requires a physical ranged weapon)

Staunch Defender - Protection Upgrade

Instead of the normal Protection stance, You can move up to your speed to an ally you can see being attacked and impose disadvantage on the attack if you can get within 10ft of the engagment. If the attack still succeeds roll a d12, the damage is mitigated by that amount. (Requires shield)

Trained Senses - Blind Fighting Upgrade

Along with the normal Blind Fighting stance, You can make a reaction attack to anything entering your blindsense range that you actively perceive. You can move up to 5ft within that range to make an attack but the area of your blindsense does not move with you until after the reaction attack.

Champion's Focus: Combat Momentum

At 15th level, you gain hardened focus in battle. 3 times per long rest, as a bonus action, during your turn you can enter into a Focused Combat state. You must use this before any other action during your turn (including saving throws) and must have at least one known enemy within 15ft (known enemy meaning non-forced or charmed target that you are aware is there). In this state, you mark one target within 15ft of you. You must make all attacks on this single target without Improved Critical or any Advantage/Disadvantage. The rolls cannot be changed or affected by any outside force. You apply your proficiency bonus to damage on all hits. If all attacks land, you apply disadvantage on any attacks made by the enemy during their next turn if they stay within 15ft of you.

Champion's Regeneration: Combat Survivor

At 18th level, you attain the pinnacle of resilience in battle. At the start of each of your turns in combat, you regain hit points equal to 5 + your Constitution Modifier (minimum of 1 hit point). You don't gain this benefit if you have 0 hit points or if you have more than half of your hit points left. Also, If you have a second wind available when you do reach 0 hit points, the second wind can be used to avoid going unconscious gaining the health of the second wind plus the survivor health.