This is a …………… on his character.

The correct answer is: Blot.

A blot is a small, dark spot or stain, especially one that spoils the appearance of something. It can also be a mistake or error. In the context of the question, a blot on his character would be something that damages his reputation or makes him look bad.

The other options are not as accurate or appropriate. A blur is a hazy or indistinct image, while a slur is a spoken word or phrase that is offensive or insulting. A spot is a small, round mark or stain, and a mark is a sign or indication of something.

Here are some examples of how the word “blot” can be used in a sentence:

• The ink blot on the paper made it difficult to read.
• The child made a blot on the tablecloth with his food.
• The politician’s recent scandal was a blot on his character.