A person who is obsessed with themselves and has an exaggerated sense of self-importance.

आत्मकेंद्रित व्यक्ति

English Usage: His egomaniac behavior made it difficult for others to work with him.

Hindi Usage: उसके आत्मकेंद्रित व्यवहार ने दूसरों के लिए उसके साथ काम करना मुश्किल कर दिया।