Mouse acceleration is a major drawback for competitive shooters, and Marvel Rivals is no exception. The game unfortunately enables mouse acceleration by default, lacking an in-game toggle. Here's how to disable it:

Since the game offers no in-game setting to disable mouse acceleration, you must directly modify the game's configuration file. This is a straightforward process:
%localappdata% and press Enter.[/Script/Engine.InputSettings]
bEnableMouseSmoothing=False
bViewAccelerationEnabled=False
You've now disabled mouse acceleration within Marvel Rivals. For optimal results, also disable mouse acceleration in Windows settings:
With mouse acceleration disabled in both the game and Windows, your aim will be significantly improved due to consistent sensitivity.

Related: Troubleshooting Marvel Rivals Issues
Mouse acceleration dynamically adjusts your mouse sensitivity based on movement speed. Faster movements result in higher sensitivity, while slower movements lead to lower sensitivity. While convenient for general use, this is detrimental to shooters like Marvel Rivals.
Consistent sensitivity is crucial for building muscle memory and improving aim. Mouse acceleration prevents this by constantly changing your sensitivity, hindering the development of precise aiming skills.
By following these steps, you can eliminate mouse acceleration and enjoy a more responsive and consistent aiming experience in Marvel Rivals.
Marvel Rivals is currently available on PS5, PC, and Xbox Series X|S.