Stun

 causes any flee will be negated and makes it impossible to move, attack, pick up items, skill usage, sitting, force disconnection, and item usage.

In Ragnarok Online II, it's is a crowd control (CC) debuff that prevents the target from making any actions, such as moving, using skills, or consuming any potions.

Abilities
The following abilities inflict :
 * Ragnarok Online
 * [Stun Attack] - An NPC-exclusive skill that inflicts by chance.
 * Raid
 * Vermilion on the Beach
 * Hammer Fall
 * Sonic Blow
 * Cracker
 * Land Mine
 * Hammer of God
 * Ragnarok Online II
 * Asura Strike
 * Shield Charge

Cure
can be cured through the following methods:
 * Ragnarok Online
 * Priest's skill Status Recovery can undo the effect.
 * VIT (greatly) and LUK (very minorly) will reduce the duration of this ailment and the chance to be inflicted. Base level will slightly lower the chance of Stun being inflicted.
 * One of Battle Chant's random effects removes all abnormal status effects from party members, including Stun status. However it can't remove the Stun status from the Paladin itself since it can't cast any skill as long as he/she is stunned.
 * One of Battle Chant's random effects grants 60 seconds of immunity to all status effects to party members, including Stun status.
 * Dispel removes this ailment.
 * Mercenary's skill Regain can undo the effect.
 * Royal Guard's King's Grace can remove the effect.
 * Ragnarok Online II

Prevention
The following lists ways that can be prevented:
 * Ragnarok Online
 * Orc Hero Card grants immunity.
 * Stalactic Golem Card increases resistance by 20%.
 * Gemini-S58 Card increases resistance by 30% if the user has 90 or more base AGI.
 * Flame Skull Card increases resistance by 30%.
 * Valkyrian Armor increases resistance by 50% if the user is Merchant, Swordsman or Thief Class.
 * Note Headphone increases resistance by 10%.
 * Dark Bacilium increases resistance by 20% + 2%*upgrade.
 * Diabolus Armor increases resistance by 5%.
 * Meteo Plate Armor increases resistance by 30%.
 * Ragnarok Online II