Many people view breakers as just incapable of properly using weapons, but you know better your mastery is simply too much for any weapon to handle, interestingly enough though it seems some people just naturally exhibit this ability when they fight regardless of training.

Smith's tools proficiency

When you take this subclass at 3rd level you gain proficiency with smith's tools, if you already have proficiency with smith's tools you can instead gain proficiency in a skill of your choice.

Twice as hard

At 3rd level you gain the ability to double your melee weapon damage dice and strength modifier at the expense of your weapon taking damage equal to your strength modifier(minimum of 1) a finesse weapon only gains this benefit when wielded with strength. The hp of your weapon is based off its weight category and whether or not it is magical, 10hp for light weapons, 20hp for regular weapons, 30hp for heavy weapons, and x3hp for a magical weapon. A weapon's hp can be restored by using smith's tools to maintain its condition over a short or long rest(non-magical only), having mending cast on it, or by paying a smith to fix it for you, if a weapon is completely broken it must be repaired at a forge over the course of a day.

Force of destruction

Starting at 7th level when you use your "twice as hard" ability to increase weapon damage the weapon is considered magical for the purpose of overcoming non-magical resistance, additionally magical weapons can be repaired using smith's tools, and your unarmed strikes deal 1d8+strength bludgeoning damage and can be affected by your "twice as hard" ability(you take the effect damage when you do this).

Sticks and stones

Starting at 10th level when you use your "twice as hard" ability you can choose to take the damage instead of your weapon, Additionally when you are hit by a weapon attack you can inflict damage to the attackers weapon equal to your constitution modifier(minimum of 1).

Broken never beaten

Starting at 15th level once per long rest when your hit points reach 0 you instead stay up on 1hp, additionally when you use this ability the damage of your weapon attacks increases as per the effect of "twice as hard" without the damage to your weapons for the next minute(this does not prevent you from using "twice as hard") afterwards you gain 1 level of exhaustion.

Worldbreaker

Starting at 18th level when you use your "twice as hard" ability you can instead choose to instantly break your weapon providing the usual benefits as well as increasing its damage by a number of d4s equal to its remaining hit points. if this ability is used with an unarmed strike you are reduced to 0 hit points after rolling damage.