Carnage

Learning how to fight was simply a means to an end for you. You crave violence, and are fueled by bloodlust. Your fervor is starting to manifest in your combat prowess. Speed allows you to close the distance to your prey, and your unbridled drive for conflict drives your blows.

Level 3: Rapid Action

At 3rd level, you can Dash or Disengage as a Bonus Action.
Additionally, when wearing medium, light, or no armor, Opportunity Attacks against you are made at disadvantage.

Level 3: Wild Strikes

Starting at 3rd level, you can throw aside all concern for defense to attack with ferocity.
When you make your first attack on your turn, you can decide to attack wildly. Doing so gives you advantage on melee weapon attack rolls using Strength or Dexterity during this turn, but attack rolls made against you have advantage until the start of your next turn.

Level 3: Death Train

At 3rd level, while in initiative, whenever you reduce a creature to 0 hit points, you increase your critical range by 1 (allowing you to critically hit on a 19 or higher) until that initiative ends.
Your critical range cannot be reduced by more than 4 using this feature, capping your critical range between 16-20.

Level 7: Mad Dash

At 7th level, your movement speed increases by 10 feet. 

Level 10: Furious Endurance

At 10th level, when you are reduced to 0 hit points but not killed outright, you can drop to 1 hit point instead. You may do this a number of times equal to half your proficiency bonus, rounded down. This feature replenishes when you complete a Long Rest.

Level 15: Bloody Harvest

At 15th level, whenever you or an ally you can see critically hits, or you reduce a creature to 0 hit points, you gain temporary hit points equal to your fighter level plus your Constitution modifier.
These temporary hit points do not stack.

Level 15: Murder Train

Any time you are benefitting from the increased critical range of your Death Train feature, allies within 60ft of you increase their critical range by 1. Allies cannot benefit from more
than one instance of Death Train.

Level 18: The Killing Field

At 18th level, slaughter is at your command. While in initiative you have the following abilities:
• You have advantage on melee attacks made against Bloodied creatures (Creatures that are at less than half their hit points).
• Temporary hit points gained from your Bloody Harvest feature can trigger when any creature within 60ft is reduced to 0 hit points, including allies.
• When any creature within 60ft is reduced to 0 hit points, you can use your reaction to move up to your speed.
• When a creature within melee range misses you with an attack, you can use your Reaction to make a single Melee Attack against them with advantage.
• If you have advantage on an attack during your turn before using Wild Strikes, you may still activate Wild Strikes. When you do so and successfully hit, you may add your proficiency bonus to a single damage roll, once per attack.