Counterstrike

Counterstrike
AO = attack of opportunity, RAW = rules as written
You can use 'Mark' and are proficient with the following weapons with the Disarm property.
(rule edit) Disarm under the general rule can only be used if a target is grappled by the aggressor.

****1.MARK****
DMG Optional rules page 271 Action Options:
Mark:RAW +
Place 1 mark on any target you attacked (regardless of success) during your turn. Remove at the start of your next turn.
AO: When you trigger an AO against your mark, it doesn't use your active reaction to use one of the following options.

Take an ordinary AO with advantage.
Grapple the target as an AO [interrupt].
Shove attack or Shove Aside as an AO [interrupt].(5' Push/knockdown or 5' slide w/ disadvantage)

If you have used your reaction you can still make an ordinary AO against your mark if triggered (no advantage or above options).
You can't take 2 AO or 2 reactions during a round.

****2.DISARM****
Disarm: RAW (DMG 271) edit +"use a weapon attack" to "use a disarm weapon attack." - Eliminate the last sentence. Disarm vs wrong size will be a penalty in either direction. One size class difference is disadvantage for the attempt, 2 is not permitted.

This activity can be used as a readied action but it isn't an interrupt. You can use this readied effect even if a weapon that attacked you is beyond your reach.

Size classes: The defender's weapon is always the size class of the user but +1 size class if the object is held in two hands.

These all have the Disarm category. [simple, martial, disarm]
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Sai/Jitte (enhanced dagger) 3 gp 1d4 piercing 1 lb. Finesse, light, monk weapon, M disarm property, L disarm property if dual-wield.
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Nunchuck (enhanced club) 2 sp 1d4 bludgeoning 2 lb. Light, monk weapon, M disarm property, L disarm property if dual-wield.
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Three piece rod aka triple-chucks (enhanced Quarterstaff) 4 sp 1d6 bludgeoning 4 lb. Versatile (1d8)
M disarm property, L disarm property if two-handed.
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Main-gauche (enhanced short sword) 15 gp 1d6 slashing 3 lb. Finesse, light, monk weapon, M disarm property, L disarm property if dual-wield.
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Flamberge (spinebone sword) 25 gp 1d10 slashing 7 lb. Heavy, two-handed, L disarm property
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Kuyari (chain-spear) 30 gp 7 lb. - monk weapon, L disarm property, Polearm master.
spear-end 1d8 piercing Finesse, reach, two-handed
Or 1d8 bludgeoning. Finesse, reach, two-handed {Variant1}
Or 1d8 slashing. Finesse, reach, two-handed {Variant2}