What are the most important accessibility features for games?

We’re currently developing a 2D Platformer and we decided to take some time to implement Accessibility Features. But we couldn’t find good information about Accessibility Features, muss less how to implenent them. With Accessibility Features we mean things like to reduce risk of seizure (Photosensitive Epilepsy). There will be a Accessibility Menu to manually activate these.

So does anybody have some Ideas what Features we could implement and some helpful tips about how to implement them?