The Mahabharata (books and TV series) always introduces any warrior as an "unmatched warrior". For example, Jarasandha is introduced as an unmatched warrior, Kichaka is introduced as an unmatched warrior, Bhishma, Dronacharya, Bheema, Arjuna and Karna are all introduced as unmatched warriors.
Frankly, I am irritated with calling every warrior "unmatched".
In my opinion, there is no definitive answer to your question. Since we cannot define the various aspects of greatness, or more specifically the various aspects of a great warrior. Every warrior has mastered the skill in his own way.
For example, consider Arjuna. Arjuna is regarded as one of the greatest archers. When Dronacharaya challenged his students, he was the only one who could shoot at the eye of the bird in only one attempt. On one occasion when Arjuna returned to his camp after the day's war, he was overcome with a sense of ego. He asked Krishna to alight the chariot first, as it is appropriate for a charioteer to get down and give a helping hand to Arjuna. Krishna did not heed to Arjuna's request. He asked Arjuna to get down first, and Arjuna finally got down first. As soon as Krishna also alighted from the chariot, the chariot burnt into flames. Arjuna was startled and asked Krishna for an explanation of such an extraordinary event. Krishna replied Arjuna very powerful arrows with great potency were fired at you. I was making sure that these deadly weapons did not immediately release their power. I have held them back. As soon as I alighted from the chariot the weapons could release their power. And the story continues...
Now if we were to look at this incident, we will understand that Bhishma, Drona, and others who fired their arrows at Arjuna were equally powerful. Arjuna was safe only because of Krishna. Could Bhishma, Drona, and Arjuna kill anyone with their powers? No. Bhishma gave up his arms because he did not want to fight against another gender. Drona gave up life by himself because he thought his son was dead. They were all "matchless" warriors and there is no way in which you can list down warriors by their greatness.
The only one who is greatest and matchless among all is Lord Krishna himself!
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