The only part he can be excused for is making the wish, imo. It is a reaction born out of his frustration with his lack of confidence, and he doesn't know that it will really work.

Once it became clear that the wish had a real effect, and he chose to ignore the real Nikki's suffering and indulge himself in the lie, he became a complete villain.

If he had instead wished for the courage to tell Nikki how he felt, completely different movie.