Monks of the Way of the Nullifying Fist have an innate interest in the mechanics behind all of the different abilities possessed by creatures. Intense study into those mechanics allows them to bypass and shut down those abilities. By spending ki points, a creature's defences are shut down one by one until the creature is nothing more than a helpless husk of what they once were.

Wear Down

At third level, you can use your knowledge of your opponent's abilities allows you to quickly wear them down. As a bonus action, you can spend 1 ki point to choose a creature within 5 feet of you as a target. Only one target can be selected at a time, when selecting a new target, they will replace your original target. On each consecutive successful attack on your target reduces their AC and max hit points by 1. A target's AC and max hit points can be reduced by a maximum of 5 times. This effect can last indefinitely unless you miss an attack, move outside of 5 feet of your target, or attack a creature other than your target.

Bypass Defence

You can take advantage of your opponent's overreliance on their abilities to punish them severely.

You can spend 1 ki point to try to knock an opponent prone with an attack, the save DC is equal to 8 + your proficiency bonus + your wisdom modifier. Add 1 to your save DC for every point of AC removed by you. If 5 or more points of AC are removed, creatures roll with disadvantage.

On an attack against a prone target, you can ignore an additional point of AC and deal an additional point of force damage for each point of AC removed by you.

Abuse of Opportunity

Knowing the innerworkings of the different creatures around you allows find and take advantage of an opportunity when it arises.

You can make a additional attack without spending an action or bonus action on a creature with 5 points of AC reduced by you, or a target with 3 or more points of AC reduced by you.

Your attacks of opportunity ignore disengage actions, and reduces the creature's movement by 5 feet for each point of AC removed by you.

Spending 1 ki point allows you to add an additional 1d4 force damage to your opportunity attack. Making an opportunity attack does not activate any ability, feat, racial trait, or spell, and you can spend an additional ki point to bypass a resistance, spell, or ongoing ability.

Nullifying Attack

Your mastery over your opponents allows you to shut down each and every ability that they have.

On an attack, you can spend 1 ki point to try and shut off a creature's abilities. The save DC for this ability is equal to 8 + your proficiency bonus + your wisdom modifier. This always succeeds on one of your targets. On a success, you can choose to disable 1 action, bonus action, free action, reaction, racial trait, class feature, or other ability that does not come from a magical item that you know of.

You can do this up to 3 times on a creature, and up to 10 times on a target.