Being inked causes characters to take more damage proportional to the coverage amount. To achieve this, there is a damage multiplier that is calculated with 1 + ink * (1.5 - 1) / 180. With this equation, the maximum damage multiplier of 1.5× is reached when the character is covered by 180 units. Characters can be covered by up to 300 units of ink, and each individual attack has its own ink cost and coverage amount. For more information on Ink, check Smash Wiki.