Like Imam Hasan (a.s), Imam Hussain (a.s) also earned accolades for his bravery during the lifetime of Amir'ul-Mu'minin (a.s) in the battles of Jamal, Siffin and Naharwan. The greatest achievement of his in this regard is the battle of Karbala’ on the day of Ashura. Hamid Ibn Muslim, a soldier of Yazid's army and the narrator of those events says, "I did not find anyone in the world more valiant than Imam Hussain (a.s). Hunger and thirst of three days, the burning sands of Karbala’ , the corpses of relatives, friends and children before his eyes, the fear of the dishonor of women, wounds in every inch of the body. None in the world could fight so bravely as Hussain did, despite all those things. The first attack mounted by Hussain had created turmoil in the Yazidite forces. People were fleeing at his sight like locusts. Imam Hussain (a.s) waged many attacks, one after the other. The result was that at very many places piles of corpses laid. His last attack was terrific. The enemy fled in such a terror that the last men of that army entered Kufa. Everywhere there were screams of: Spare us! Spare us! O son of the Messenger of Allah! Seeing their wretched condition the son of the Mercy of the worlds had pity on them and put his sword in its sheath. Now it was time to display gems of patience.

SOURCE:

1. Book named "Akhlaq al-A’imma, Morals & Manners of the Holy Imams" by author Maulana Sayyid Zafar Hasan Amrohi.

2. Al-islam.org (https://www.al-islam.org/akhlaq-al-aimma-morals-manners-holy-imams-maulana-sayyid-zafar-hasan-amrohi)