Why is Ayatollah Khomeini important in history?

The biggest Iranian Revolution first started by students and middle class seen overthrown of the last autocratic king Shah Iran (Mohammad Reza Pahlavi), and the return of 15 years in exile of Ayatollah Khomeini, being upped as the first people's choice leader of 1979 Iranian Revolution.
As by the west and its allies, Ayatollah Khomeini actually seen as the perfect pious and peaceful character to be, but when Ayatollah Khomeini takes his leader role, he seems to be bigger than himself and sharply be the one responsible spreading the anti-Israel anti-US and instead of just lead Iranian to a peaceful living after the revolution, Ayatollah Khomeini actually gone further actively ready to war with everybody that preventing Iran from rising again as significant political power.

He dies in 1986, but his pious potraits can be seen till today being painted in large sizes on some buildings towards the Syuhada Square in Iran central town.