besmirch
Definitions
To damage the reputation of someone or something in the opinion of others.
To make something dirty or discolored; to soil.
Examples
The politician tried to besmirch his opponent's reputation with a series of false accusations.
She refused to let the scandal besmirch the hard-earned legacy of her family.
He felt that the graffiti on the monument served only to besmirch the memory of the fallen soldiers.