Unfortunately filing complaints in Chicago doesn't result in discipline towards on officer. If a complaint is sustained by COPA (the agency responsible for accepting and investigating complaints) then COPA gets to make a "recommendation" to the Chicago Police Department with how to discipline the officer involved. It is then up to CPD whether they want to actually follow that recommendation or not. A separate but related issues is that officers also don't always oblige to requests for their identification in the event of an altercation.

Source: Chicago resident who has filed complaints