Mahatma Gandhi [Ideological leader]:

When you look back for great leaders in the past, you can see Mahatma Gandhi as an introvert. Though being an introvert he was an ideological leader of India and still at present he has many followers who believe in non-violence in the world. He showed us that we can achieve victory even by remaining peaceful. He had credited for launching one of the biggest mass movements in the history. As you remember, even the present U.S. President Barack Obama had once told he is a firm believer of Gandhian thoughts. 

Albert Einstein [Theoretical Physicist]:

Even though Albert Einstein is considered as a skilled introvert, he was a master when it came to obsessive interest and perfectly balanced love of loneliness and kindness. He is considered as the father of “Modern Physics” and prolific intellects in human history. He is also remembered for his discovery of law of the photoelectric effect and he had also won the Nobel Prize for that in the year 1921.