Anti-skill means that a hero is able to disable skilled usage of any category of skill (game sense, ability usage or mechanical skill) through a fairly bullshizzle mechanic. An example of this is a Soldier 76 perfectly tracking a Baptiste at long range, but before he dies Baptiste simply presses e for immortality. Hack and emp are abilities that do this. Not only that but infinite stealth and translocater take away a lot of the skill Sombra used to have.