Too gras for the coup de grâce
Mistaking grace and gras is often made by English-speakers. I suspect it’s because they just don’t grasp the meaning of gras which simply translates into fat. Therefore doesn’t make sense in the present context. So, when using this expression, grâce which means mercy, must be pronounced grass. Although, thinking about it coup de gras could turn out to be the coup de gâce.