Black powdery or flaky substance produced by the incomplete burning of organic matter.

In a metaphorical sense, it can refer to something that darkens or sullies one's reputation.

कलंक

English Usage: The scandal left a soot on his otherwise clean reputation.

Hindi Usage: स्कैंडल ने उसकी अन्यथा साफ़ प्रतिष्ठा पर कलंक छोड़ दिया।

To cover or smear with soot.

To make dirty or unclean, often in a figurative sense.

गंदा करना

English Usage: He felt that lying would soot his conscience.

Hindi Usage: उसे लगा कि झूठ बोलने से उसकी अंतरात्मा गंदा हो जाएगी।