He acts like he is the master of the universe.
Master of the Universe
idiomA powerful person.
Origin
first recorded 20th c.The "highly successful business person" sense is derived from Mattel's Masters of the Universe toy line and media franchise, which was launched in 1982. It was first used as such in the 1987 novel The Bonfire of the Vanities by Tom Wolfe (see quotations).
The CEO walked into the room like the master of the universe, expecting everyone to follow his orders immediately.
The young trader believed he was the master of the universe, but the sudden market crash quickly humbled his arrogance.