The verb marred is the past tense of mar which means to damage, spoil or ruin the figure or wholeness of something.
Synonyms are impair, wreck, blemish, or destroy.
The word origins from the Middle English (early 13th century) merren meaning “to deface, disfigure, impair in form or substance” and Old English merran (Anglian), mierran (West Saxon) meaning “to waste or spoil” and from Proto-Germanic marzjan as well as Old Frisian meria. It also comes from the Old High German marren meaning “to hinder, obstruct” and Gothic marzjan meaning “to hinder, offend”.
The strong wind marred the tent that the family had just set up.
They were fighting so he marred his sister’s painting.
His poor acting marred the beautiful story line of the movie.