Egomaniac (noun)

1. A person who is extremely self-centered or self-absorbed.
2. A person who is obsessed with their own power, talents or achievements.
3. A person who has an excessive sense of self-importance.

Origin:

From the latin word "ego" meaning "i" and the greek word "mania" meaning "madness or excessive enthusiasm". it entered the english language in the 19th century.

Examples:

1. He was considered an egomaniac as he constantly bragged about his accomplishments.
2. She was known as an egomaniac, always putting herself first.
3. The CEO's egomaniac behavior caused many problems in the company.
4. The egomaniac's demands were impossible to meet.
5. He was called an egomaniac because of his constant need for attention.