Wicked Cat is a Cat-turned-Aku. He is introduced in the Wicked Cat event, which is unlocked after clearing Arcane Confluence. Although Brainwashed Cat is visually an allied counterpart of Wicked Cat, he is not obtained by defeating this enemy, but rather from seasonal Rare Cat Capsule events.
Wicked Cat is basically a nerfed Crazed Cat with the Aku trait and a very frail Shield. His health and DPS are not that high and his range is fairly short, the Shield is also expected to break easily. Wicked Cat also has a surprisingly high knockback count of 30, resulting in many, many Shield regenerations.
Due to the constant knockbacks and Shield regeneration, the use of Shield Piercing units and crowd-controllers is not recommended. Rather, if possible, focus on raw power.
In Infernal TowerFloor 44, Wicked Cat takes 2 minutes and 40 seconds to spawn, which is enough time to rush down Hannya before he shows up. With Hannya gone, you can safely strike Wicked Cat with whatever attackers you were using against the rest of the enemies.
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