This is for advanced users. Do not use this if you are uncomfortable with third-party software injection.
Min Brightness (Black Level): This is the "washout" killer. If your blacks aren't deep, lower this value. On OLED screens, this should almost always be at the lowest possible setting to ensure true blacks. Hardware and Driver Solutions
Disable the in-game HDR toggle. Windows will often prompt that it is applying Auto HDR when you launch the game, providing better tonemapping than the native engine.