WCAG doesn't define a maximum contrast.
edit:
Interesting discussion about the effect of fonts, dyslexia, and dark-mode wrt "too much contrast" in this UX StackExchange thread. https://ux.stackexchange.com/questions/123504/maximum-contra...
edit:
Interesting discussion about the effect of fonts, dyslexia, and dark-mode wrt "too much contrast" in this UX StackExchange thread. https://ux.stackexchange.com/questions/123504/maximum-contra...