The Knightmare Fighter

You are a knight, the person or persons you serve use you when an example must be made. You have undergone training with heavy weapons and armour that would break most people. 

Knightmare Training

While in Heavy armour and using a two-handed weapon you reduce bludgeoning, piercing, and slashing damage by 1.
When you acquire an extra attack the reduction increases by one for a total of 4 at the 20th level. 
This stacks with the Heavy Armour Master feat.
Additionally wearing heavy armour doesn't impose disadvantage on Dexterity (Stealth) checks.

Terrifying Follow-up

When you take the attack action all attacks after the first deal double your strength bonus on damage rolls

Leveraging Reach

On your turn when you take the attack action with a Heavy weapon you may increase your reach by 5ft 

Mighty Swings

Starting at 15th level,  When you take the attack action you must decide if you are going to use this feature. You make all your attacks at a -4 to hit to deal +8 bonus damage when using a weapon two-handed. At 20th level the penalty is increased to -6 and the bonus damage is +12
This can stack with the Great Weapon Master Feat.

Titanic Blow

18th Level: You can use your action to make a single attack. You make this with a -5 to hit. If this hits it's treated as a critical hit. If it hit and the natural roll would have been a critical hit double the critical dice