Champion's Training.

The archetypal Champion focuses on the development of raw physical power honed to deadly perfection. Those who model themselves on this archetype combine rigorous training with physical excellence to deal devastating blows.

Level 3 Features:

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.

Remarkable Athlete.

Also at 3rd level, you gain proficiency in the Athletics skill if you don't already have it. Your proficiency bonus is doubled for any ability check you make that uses this proficiency.
Additionally, you can add half your proficiency bonus (rounded up) to any Strength, Dexterity, or Constitution check you make that doesn't already use your proficiency bonus.

Level 7 Feature:

Impeccable Footwork.

At 7th level, climbing and swimming no longer cost you extra movement and you gain proficiency in Dexterity saving throws.

Level 10 Feature:

Additional Fighting Style.

At 10th level, you can choose a second option from the Fighting Style class feature. You can choose to replace this Fighting Style with another Fighting Style option available to fighters each time you complete a long rest.

Level 15 Feature:

Superior Critical.

Starting at 15th level, your weapon attacks score a critical hit on a roll of 18-20. When you score a critical hit with a weapon attack, you gain advantage on all weapon attacks you make before the end of the current turn.

Level 18 Feature:

Survivor.

At 18th level, you attain the pinnacle of resilience in battle. At the start of each of your turns, you regain hit points equal to 5+ your Constitution modifier if you have no more than half of your hit points left. You don't gain this benefit if you have 0 hit points.