Badly poisons the target, dealing more damage every turn.

Toxic causes the target to be badly poisoned. Pokémon that are badly poisoned will lose an increasing amount of HP at the end of each turn.
The affected Pokémon will lose 6,25% (¹⁄₁₆) of its maximum HP at the end of the turn increasing by by 6,25% each turn.
The table below shows the amount lost per turn:

Turn	Amount	Total Lost
1	6,25%	6,25%
2	12,5%	18,75%
3	18,75%	37,5%
4	25%	62,5%
5	31,25%	93,75%
6	37,5%	131,25%

Toxic doesn't work if:

• the target is already carrying a major status ailment
• the target is behind a Substitute
• the target is a Poison or Steel-type Pokémon
• the target has the ability Immunity

If used by a Poison-type Pokémon, Toxic will always hit, even if the target is in the semi-invulnerable stage of Bounce, Dig, Dive, Fly, Phantom Force, Shadow Force or Sky Drop.

• In Gen 1 Toxic also increase the damage taken by Leech Seed due to a bug.
  The badly poisened effect will become regular poison outside of battle.
• In Gen 1-4 Toxic has 85% accuracy
• Dynamax Pokémon in Max Raid Battles and Tera Pokémon in Tera Raid Battles will receive regular poison instead.