Kunkka only deals Quell bonus damage as long as Tidebringer is on cooldown
As long as Kunkka does not skill Tidebringer
, the bonus damage is not applied. The bonus damage is no applied during the attack itself as well, which might be intended. Lastly the Quell bonus damage is not applied when the ability is skilled, off-cooldown and not used in the current attack (normal attack without auto cast or manual cast).