There are a few attacks in Super Smash Bros. Ultimate that have a poison effect. The poison effect acts similarly to the Flower effect, which makes opponents hit by the effect slowly take damage for a while. Any fighter that is hit by a poison attack will have a purple tint and purple bubbles rising from them while they take damage. Opponents who are under the effects of poison might display an angry expression, surprised expression or sad expression.
In addition to all the attacks that normally inflict poison on opponents, there is an Adventure Skill in World of Light that gives all smash attacks a chance of having this effect. Certain Spirit battles will have a stage with a poison floor or poison fog.
List of poisoning attacks
By enemies and bosses