As of right now, whenever a monster gets cursed, all they do is keep on attacking. Of course this gets them damaged, but with "Cursed AI" a monster has a random chance of getting a special cursed attack. For example:

Wolver (regular one) gets cursed. Instead of the normal single-bite attack, the Wolver will have a chance (say 30%) of drawing a "Cursed AI" attack, for example, a triple-bite attack like an Alpha Wolver's that deals the flingback damage of only one individual bite. That is to say, the Cursed AI attack does not make the monster take any more damage than it would do from dealing a normal attack. However, this chance for a Cursed AI attack would make cursing monsters a little more interesting, and might fix the Lumber's curse-resistance.

A few Cursed-AI ideas I had in mind:
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Fiends/Undead: Immune
Beasts:
-Wolvers: Listed above.
-Chromalisks: Instead of spitting or Tongue-ing, the Chromalisk has a chance to rush forward and headbutt the Knight dealing damage and status. This headbutt tracks much like the former Wolver attacks and modern Devilite missile attacks, giving it a lower chance to miss.
-Snarbolax: I'm not sure if you can curse Snarby (regular), but if so, his Cursed AI attack would be immunity to the bell (so even if the bell is hit, he would not be stunned)

Constructs:
-Battlepods: Don't know if Battlepods can e cursed, but if so: Each attack has a chance of generating Gremlin Bombs within a 2-square radius surrounding the Battlepod.
-Gun Puppy: A cursed Gun Puppy will shoot rocket-like projectiles instead of orb-like projectiles. These projectiles home in on players like a Rocket puppy.
-Rocket Puppy: Put into a second category due to the unique nature of its' attack; Rocket Puppy AI will involve 3 homing rockets being fired instead of one
-Lumber: A Lumber will charge the player using its good arm as lead (much like the Chargers in L4D2) and inflict elemental and status damage. This attack follows the tracking AI of Devilite missiles
-Mecha Knights: A Mecha Knight will release a Brandish-like wave of attacks, the length of which depends on the Tier (Tier 1-3, Tier 2-4, Tier 3- 5 Squares)
-Retrode: A Retrode will fire, instead of a single beam, a ray of 3 beams that wash out in front of it
-Scuttlebots: A Scuttlebot will act as a kamikaze bomber, detonating itself with enough force to take out any non-UV'd shield it happens upon
-Roarmulus Twins: In addition to the regular AI, the Roarmulus Twins will have a very low chance of summoning 2-4 Gremlin Menders to heal them.

Gremlins:
-Thwackers: Thwackers will be buffed with increased speed, allowing them to move faster for the next 10 seconds. This attack does not do any damage.
- Menders: Menders will call upon an extremely rare AI which allows them to sacrifice themselves and revive all deceased Gremlins within a 3-square radius.
- Scorchers: Scorchers will have a low chance to create a patch of shadow fire spanning 3-5 blocks (depends on tier)
-Demo: Demo Gremlins will have a low chance to spawn a 'sticky bomb', which moves toward the nearest player and detonates like a regular bomb
-Knocker: Knockers will have the ability to send a wave of explosions down their sticks, spanning 3-5 blocks (Depends on tier)
-Mortafires: Mortafires will now be able to drop bombs in a circle around them, as well as fire their weapon
-Ghostmanes: Ghostmanes will, in exchange for their health, gain the ability to instant-deathmark a knight before they attack.
-Seerus: Seerus will, in place of his diagonal attack, send a radius of explosions around him for 3-5 blocks (depends on tier)

Slimes:
-Jellies: Jellies will have a chance of an extended-range spike attack that behaves much like that of the Snarbolax, which spans 3-5 tiles (Depending on tier)
-Lichens: Lichens will be able to fire spikes, much like their Unknown Passage counterparts, that inflict elemental and status damage.
-Large Lichens: Large Lichens will be able to spawn small, uncursed lichens, at a cost of their HP
-Polyps: Polyps will fire one spread of three larger spikes, each of which does 1.5x the damage of a normal spike and has a 100% chance of status
Royal Jelly/Ice Queen- If this boss is cursed, their mini-jellies will immediately stop flocking toward her and turn on the nearest Knight
-Mini Jelly- The Mini-Jelly has a very low chance of upgrading into a larger, normal Jelly when cursed.