Mahā-ratha means... Mahā-ratha, ati-ratha, eka-ratha. A fighter who can fight with one man, he is called eka-ratha. And one who can fight with thousands of men, he is called mahā-ratha.
The Battle of Kurukṣetra was forced upon the Pāṇḍavas by the Kurus. Still, Arjuna was not willing to kill them. Just see. He's Vaiṣṇava. He never thought of, that "My, these cousin-brothers, they have given us so much trouble. Why I shall be sympathetic upon them?" No. Still, he was sympathetic. Why? Now, because he was a Vaiṣṇava. That is Vaiṣṇava. Para-duḥkha-duhkhī kṛpāmbudhir yas tam ahaṁ prapadye (CC Madhya 6.254). Vaiṣṇava is so tolerant. They suffer; still, they do not want others' suffering. So this is Vaiṣṇava.
So in that battlefield, mṛdhe mṛdhe, there were Bhīṣmadeva, Droṇācārya, Karṇa, Kṛpācārya. They were so big fighters, mahā-ratha. Mahā-ratha means... Mahā-ratha, ati-ratha, eka-ratha. A fighter who can fight with one man, he is called eka-ratha. And one who can fight with thousands of men, he is called mahā-ratha. And more than that, he is called ati-ratha. So these generals, Bhīṣmadeva, Karṇadeva, Karṇa and others, they were very, very powerful than Arjuna. Therefore Arjuna took the opportunity of killing Karṇa in a precarious position. Similarly, Bhīṣma was... Karṇa was almost dead when Bhīṣma was fighting. So Bhīṣma promised that "Today, either Arjuna will die or his dear friend, Kṛṣṇa, will have to break His promise. Then I'll give up this fight." So Arjuna was almost shattered, his chariot broken, and he was exasperated. So at that time Kṛṣṇa took one wheel and went to kill Bhīṣmadeva. So Bhīṣmadeva saw that "Kṛṣṇa has broken His promise. Therefore I give up this fight." Kṛṣṇa came to threaten him. That means He has broken His promise. "So I wanted to see that Kṛṣṇa breaks." This is also affection, love, between devotee... Just like in sporting, just like you want to see your friend defeated, but that does not mean you are enemy. In sporting, there is fight. That one party is defeated. That does (not) mean they are enemies. Next moment, they shake hands, sit together, dine together. It is like that.