He is the freeman who could prove that you as a man can stay against
cruelty, injustice, tyrannous and tyranny.
Yes, he is the third Imam (leader) of the Sheyeh (one of the branches of Islam)
He is the son of Ali the famous man of Justice. But in my opinion he is the leader of all in the world because he showed this important fact in Karbala which we should stand against injustice.
In fact, in that time humanity needs some one to wake him up and this time also since ruler of that time was a dissolute and deceitful man. So Imam decided to stand against him so he went to him by his friends (700-800).and there happened a tremendous war which they killed Imam and his friends but they could prove their manhood by resisting the enemy. However they had been killed but the fact of the matter is they drove out them from the field and showed the truth and reality to all. In any way I can't say any thing about him or his friends. Just this quotation by Imam Hossain:
"If you don’t have religious at least live as a generous and free man