blot
n. countablen. a dirty mark or a stain, often made by ink or liquid. It can also mean something that spoils the beauty of a place or a person's reputation.
n. a spot or stain, particularly one made by ink on paper; figuratively, a blemish that detracts from a reputation or a landscape.
There is a large ink blot on my notebook.
The new factory was considered a blot on the beautiful countryside by the local residents.
The scandal remained a permanent blot on his otherwise distinguished political career, overshadowing his legislative achievements for decades.
From Middle English blot (“blot, spot, stain, blemish”). Perhaps from Old Norse *blettr (“blot, stain”) (only attested in documents from after Old Norse transitioned to Icelandic blettur), or from Old French bloche (“clod of earth”).
Often used in the metaphorical phrase 'a blot on the landscape' to describe an ugly building or structure.