The Titanblade

The Titanblade is a fighter who has acquired or forged an enormous melee weapon that is far larger than the typical weapons wielded by warriors. This immense weapon grants them tremendous power and the ability to strike fear into their enemies.

Oversized Weapon Master

You have trained to master the use of weapons that are far larger than most could handle.

• You gain proficiency with oversized weapons. An oversized weapon is any melee weapon that is intended for a creature at least one size category larger than you (e.g. a greatsword crafted for a Large or bigger creature).
• When wielding an oversized weapon, treat your Strength score as 2 points higher for the purpose of attack and damage rolls with that weapon.
• You can only wield one oversized weapon at a time, and you must wield use both hands to do so, regardless of the weapon's original properties. If the weapons typically has the "two-handed" property for its intended size category, you cannot wield it at all if you are more than one size category smaller than that intended size.

Titansmith

Your expertise as a weaponsmith allows you to modify regular-sized weapons into oversized ones. You become proficient with Smith tools if you aren't already. 

During a long rest, you can choose one regular-sized melee weapon in your possession. By expending materials worth 100 gold pieces and working on it during your long rest, you can turn the weapon into an oversized version of itself. An oversized weapon created in this way keeps all magical benefits, if any. The process doesn't create a new magical weapon; only modifies it's size.

Sweeping Cleave

As an action, you can make a sweeping attack with your oversized weapon. You make a single attack roll against all creatures within a 10-foot cone in front of you. Each target hit takes damage as if they were struck by your oversized weapon. You can use this feature a number of times equal to your Strength modifier (minimum of 1), regaining expended uses after a short or long rest.

Colossal Resilience

You have developed exceptional strength and endurance from wielding colossal weapons. Your hit point maximum increases by 1 for each fighter level you have.

Colossal Onslaught

You've honed your mastery of the oversized weapon to deliver a devastating series of strikes. Once per short or long rest, as an action, you can initiate a Colossal Onslaught. During the Colossal Onslaught, you make all of your attacks in quick succession against one opponent. If all attacks hit, you deal an additional 3d10 damage of the weapon's damage type. If any of the attacks miss, the Colossal Onslaught ends immediately.

Earthshaker

Your mastery over your colossal weapon allows you to channel the power of the earth itself.

Whenever you score a critical hit with an attack using your oversized weapon, you can choose to unleash Earthshaker's Fury as a bonus action. When you do so, the ground trembles beneath you, and you strike the earth with your weapon. A shockwave radiates out from you in a 30-foot radius. All creatures in that area must make a Strength saving throw (DC 8 + your Strength modifier + your proficiency bonus) or be knocked prone and take 8d10 bludgeoning damage. On a successful save, they take half damage and are not knocked prone.

After using Earthshaker's Fury, you can't use it again until you finish a long rest.