Colossal Weapon Master

Due to your incredible physical strength and prowess, you can now make and use weapons much larger than most others would normally dream. You can make great weapons even greater, and focus all of your being into single, earth shattering strikes. 

Colossal Weaponry

When you choose this class at 3rd level.

Using twice the time, money and resources normally used to make them, you can instead create a colossal variant of greatswords, greataxes, lances and mauls. These weapons, as the name "colossal" suggests, are much larger than normal, and can deal even more damage when used properly. 

Each time initiative is rolled, you gain 2 devastating blows. You can have 3 stored at any given time and lose all devastating blows on a long rest. You can use an action to expend one devastating blow and begin to charge an attack with a colossal weapon. You can charge an attack for up to 3 rounds (including the round you started charging). Your movement speed is zero while charging. Gain a +1 bonus to hit on your next attack per round spent charging. While charging, you can use your action to execute your blow. Roll to hit a target within range, if your blow lands, roll ALL of the damage dice you could have rolled had you attacked each of the turns you spent charging (including all extra attacks). You cannot take the attack action or opportunity attack reaction without canceling the charge and wasting your devastating blow. You can still take other actions like dodging. You can also still use your bonus actions that don't require attacking first, such as the feinting attack maneuver. If you spend 3 rounds charging and do not execute your blow the very next round, you lose your devastating blow and all charge.

Additionally, each type of colossal weapon has a special ability that comes with charging an attack with it. They go as follows: 

• Colossal Greatsword. While charging, if an enemy provokes an opportunity attack from you, you can use your reaction to refund your devastating blow and sweep their legs, dealing 4d4 and knocking them prone on hit. Additionally, your devastating blows deal an extra 2d6 per round spent charging.
• Colossal Greataxe. When executing your devastating blow, choose up to 2 targets in range and cleave them both. Deal an extra 1d6 per round spent charging.
• Colossal Lance. When executing your devastating blow, you can move up to half of your walking speed as part of the action before attacking. You can hit 2 enemies in a straight line from you within range. Additionally, you do not have disadvantage when using your devastating blow on an enemy within 5 feet of you.
• Colossal Maul. When charging, you can use your bonus action to take a single step and move 5 feet. When executing your fatal blow, deal an extra 2d6 per round spent charging, push your target 5ft per round spent charging and knock them prone.

When using a colossal weapon, you do not attack multiple times with "extra attack". Instead, you make one attack with the damage of all of the possible attacks.

Imposing stature

At 7th level, you can choose to be counted as a large creature for any reason, so long as you are carrying a colossal weapon.

You gain proficiency in intimidation while carrying a colossal weapon. 

You can add half of your proficiency bonus to all strength checks and saves.

Your first colossal weapon attack each turn deals 1d6 extra damage

A big deal

At 10th level all colossal weapons gain additional benefits:

• Colossal Greatsword. This weapon now has reach when you use it. When you use your leg sweep reaction, you can choose to not refund your devastating blow. Instead, you can continue your charge. If your leg sweep hits, your target is knocked prone within your attack range and loses 25 feet of movement for the round. You can do this once per blow.
• Colossal Greataxe. When you execute your devastating blow, you can choose to perform a destructive spin instead of cleaving 2 enemies. The spin will move you 5ft in any direction and hit all creatures within 5ft of the start and end points.
• Colossal Lance. You can now commission or make a colossal shield (+2 ac). The colossal lance can now be wielded with one hand. If the colossal shield is held,  you gain an additional +2 ac while charging, and opportunity attacks against you while you move during your devastating blow have disadvantage.
• Colossal Maul. While charging, you can use your action to roll 10 feet in a straight line. You are immune to opportunity attacks while rolling. If you push a creature into a wall or another creature with your blow, all of the creatures involved take 1d6 bludgeoning damage.

Gain an additional devastating blow every initiative roll. Add one to the max number of devastating blows you can hold.

Massively Martial

At level 15 devastating blows gain an additional 1d6 damage per round charged. Each colossal weapon gains a new ability:

• Colossal Greatsword. While charging, you can use an action and spend another devastating blow to execute your charged blow twice. Additionally, you can now opportunity attack with your charged attack if you so please.
• Colossal Greataxe. While charging, you can use an action and spend another devastating blow to spin and throw your axe using its great momentum, hitting all creatures within 5ft of you as well as in a line up to 40ft long. Your axe will plant itself in the ground at the end of this line, unable to be moved by anyone but you. 
• Colossal Lance. While charging, you can use an action and spend another devastating blow to execute your charged blow with twice as much walking distance. While walking as part of the action, deal the charged damage to all enemies you walk through. Each enemy you walk through is pushed 5ft to either side. You can hit each creature only once with this attack, and again with the attack at the end of the move. Additionally, your range with the lance is now 15ft
• Colossal Maul. While charging, you can use an action and spend another devastating blow to slam a space within 5ft of you. If a creature is on this space, it is attacked by your charged blow. Whether or not there is a creature on the space, you shake the earth in a 40ft cube centered on you. All creatures in this area must succeed a dc15 dexterity saving throw or take half of the charged damage and be knocked prone.

Gain an additional devastating blow each initiative roll.

Hulking Figure

At level 18.

All the time you've spent using absurdly heavy weapons has earned you an incredibly strong physique. If it is currently lower, your strength score is set to 18. 

While charging, you have resistance to all physical damage lower than half of your max health.

Once per short rest, you can grab a weapon or similarly sized item, and simply mangle it beyond use with your bare hands. If its being held by someone, make a competing strength check against them to take it from them. Taking and breaking take one action total to do. You can also choose to mangle it into something useful. For example, you could take someone's sword and mangle it into a crude grappling hook.