I have been accused _____ many things in my life, but never of cowardice.

For

With

"I have been accused of many things in my life, but never of cowardice."

مجھ پر زندگی میں بہت سے الزامات لگائے گئے، لیکن کبھی بزدلی کا۔

This is a idiomatic expression, "accused of" means to be charged or blamed for something.