Brutalist

The brutalist subclass of fighter is a fighter the focuses their combat style on aggressive, brutal tactics meant to terrify those around them. Their abilities focus on stronger attacks, endurance, and inducing the Frightened condition in foes. This subclass builds on the Fighter classes natural strengths, while also adding a few features that bring fighters more into roleplay as strong, intimidating characters. 

Brutal Strikes

Starting at 3rd level, once per turn, when landing a melee attack you can choose to strike brutally. This attack deals an extra 1d6 damage of the weapon's type. If the weapon has multiple damage types, choose one to enhance. This damage increases to 1d8 at 5th level, 1d10 at 10th level, and 1d12 at 15th level. 

Intimidating Stance

Starting at 3rd level, your brutal nature effects the perception of those around you. You gain proficiency in the Intimidation skill, and can choose to roll it as a Strength (Intimidation) check rather than a Charisma (Intimidation) check, provided that your DM feels it is appropriate. If you already have proficiency in Intimidation skill, you can choose to take proficiency in another of the Fighter classes proficiency options.

Brutalize

Upon reaching 7th level, you gain the Brutalize feature. You can use this feature once between long rests. When you take the Attack action, and reduce a creature to 0 hit points, you can choose to Brutalize that creature. Brutalizing the creature takes either a Bonus Action, or you may use one of your remaining attacks from the Extra Attack feature. The brutalized creature, rather than making death saves is immediately killed. All other creatures within 30 feet who can see you must make a wisdom save against your brutalize DC, being 8+proficiency bonus+Strength modifier. Allies make this save with advantage. Any creatures who fail the save are Frightened of you for 30 seconds. 

Brutish Strength

Beginning at 10th level, you gain a pool of dice equal to your proficiency bonus. These dice match your Brutal Strike dice. When you make a saving throw or ability check you can expend a charge to add a roll of your brutal strike die to the roll. You gain all charges back on a long rest. These charges can be used on death saving throws as well. If using a charge increases your death save roll above 20, it can be treated as rolling a 20 and you regain consciousness with 1 hit point. 

Enhanced Brutalize

Starting at 15th level, your brutalize becomes even more ferocious. The Brutalize feature can now be used 2 times between long rests, and no longer takes a bonus action or attack to use. It still requires reducing a creature to 0 hit points during an attack action. The range of this effect increases to 60 feet, and can effect creatures who cannot see it, so long as they can hear it. Enemies who both directly see and hear the brutalize make their wisdom save with disadvantage. Allies no longer need to make a save against the effect. Additionally, the frightened condition is extended to 60 seconds on a failed save. 

Survivor

Your strength allows you to carry on beyond normal limits. At the start of your turn, you regain hit points equal to your strength modifier + your constitution modifier, provided your current hit points are below 50% of your max hit points. You don't gain this benefit if you have 0 hit points, or have more than half your maximum hit points.