Billy's poison is accompanied by intense pain and suffering, as if activated by his anger and resentment. His venom slowly torments his opponents, causing fear and despair in them as they grow weaker.

His ability is "CHIRONEX"
It is a characteristic that aggravates the poisoned state and has two effects. If you trigger the additional effect with a poison attack on an already poisoned enemy, the enemy's poison state will progress to a highly poisonous state. In addition, if you poison an enemy in a poisonous state, you can bring them down regardless of their HP.
The other is to deal poison damage every second during the waiting screen.