RaidCodex
All buffs and debuffs

Debuff

Weaken

Increases damage received by the Target Champion by 15% or 25%.

What the game's own status effects screen says

In the game data this effect appears as IncreaseDamageTaken25, IncreaseDamageTaken15.

Champions that apply it

138 champions have a skill that applies Weaken, according to the effect lines in the game data. This lists who applies it, not how reliably: chance, duration and resistance are on each champion's page.

The description is the game's own text. It has not been tested in battle here, and the game's wording can be loose (for example about numbers that differ between versions of an effect). See Data quality for what has and has not been checked. Found a mistake? Use "Report a problem" at the bottom of the page.