Ranking of Mahabharata warriors SOLELY based on pure skills. Shree Krishna and Balarama cannot be part of the comparision as they both are gods. Hanumanji and Parshuramni also belonged to Treta yug.
1) ARJUNA.
Among all the warriors of Mahabharata Arjuna had maximum achievements. Arjuna was the best archer of the era with technique of shooting in the dark. Killed powerful demons like Nivatkavachas 14000 Kalkeiya and Poulama demons and defeated Devas headed by Indra in Khandava dahana along with Krishna. Was most destructive warrior in Kurukshetra war and killed several soldiers and warriors. Arjuna killed 7 akshauhini armies of Kauravas on 14th day. Possessed the five techniques of archery. Defeated Bhishma, Drona and Karna in Virat war and again in Kurukshetra war plethora of times.
2) ABHIMANYU
He defeated Drona, Karna, Ashwathama and other Kaurava warriors on 13th day. He was the only warrior in Mahabharata besides Arjuna, Krishna and Pradyumna who knew the knowledge of chakravyuh. Many people think that Abhimanyu,’ s performance on 13th day was due to boon. Boon is an interpolation and has been removed from the critical edition.
Also Abhimanyu performed impressively on other days too. He overpowered Bhishma and sliced down his standard. Bhishma was forced to call divine weapons to counter Abhimanyu despite being protected by 5 maharathas. On the 4th day, Abhimanyu fought Ashwatthma, Shalya, Bhurishrava etc and gained the upper hand. On the 9th day, Abhimanyu alone overpowered Drona, Kripa, Ashwathama, Bhurishrava and Jayadratha and scattered the Kaurava army. He then also defeated Alambusha the rakshasa who was skilled in Maya.
This is my opinion that most of Bhagadatta's exploits and victories over Abhimanyu are because of his powerful elephant, and in pure archery skills he is well behind that of Abhimanyu based on his 13th day performance. Also Abhimanyu was repeatedly stated to be equal to that of Arjuna.
3) DRONACHARYA.
Quite powerful warrior despite being weakened due to old age. He possessed powerful celestial weapons like Brahmashirastra, Narayanastra and Vajrastra. Killed prominent warriors from pandava side like Drupada, Virata, Shankha, Dhrishtakeu, Brihadrakshatra etc. The only warrior who managed to put up a good fight to Arjuna on 14th day. He was the best in building battle formations and Pandavas needed plot armour to counter his battle strategy on one particular day ie Shiva,’ s boon on 14th day. On 15th day he was invincible and even the saptarishis had to arrive to stop him from destroying the Pandava army such that Pandavas had to use treachery to bring him down.
4) ASHWATHAMA/KARNA(Tied)
Ashwathama
Son of Drona and underrated as a warrior. Possessed celestial weapons like Narayanastra and Brahmashirastra. He was the only warrior who stalemated Arjuna in Virat war where other warriors failed against Arjuna and performed a superhuman feat of breaking the string of Arjuna,’ s Gandiva. Defeated Ghatotkacha and killed his son Anjanparvan and shattered his entire fleet of rakshasas.
On 15th day he invoked Narayanastra and forced the entire Pandava army to surrender in front of him. Later unleashed Agneyastra and killed one akshauhini army of Pandavas. Was the most powerful Kaurava warrior when Mahadev entered his body.
Karna
He was the student of Parshurama and an excellent warrior. Countered most number of group attacks from Kaurava side. Defetaed and spared Yudhishthira on 17th day and could have won the battle by capturing him but allowed him to escape due to his promise to Kunti. Gave Arjuna the toughest fight and almost killed him with Nag dart. Karna was nearly invincible on 17th day with the celestial Vijaya bow of Parshurama and repeatedly baffled all weapons of Arjuna including Vajratra, Brahmastra and Aindrastra(which defeated the entire kaurava army on 3rd day.)
Defeated Jarasandha in wrestling fight and spared him. Cleared 1000 illusions of Ghatotkacha during night time and finally killed him with infalliable Vasavi shakti.
Aswathamma is little superior to Karna…
But only by a small/tiny margin…
Both are equally powerful when In comes to skills but Aswathamma was the more destructive warrior and possessed many powerful weapons.
6) PITAMAHA BHISHMA
Defeated Parshurama after 24 days battle during his prime years. Defeated all the kings during Kashi swamvyara and even Jarasandha who caused terror among Yadavas and ancient kings did not attack Hastinapura due to fear of Bhishma.
He held the Kaurava army for ten days and killed 10000 warriors per day and Pandavas were not able to kill any prominent warrior from Kaurava side during his tenure as a commander. He was near invincible on 9th day when provoked by Duryodhana and wrecked havoc in the Pandava army even forcing Krishna to lift up weapon. Only warrior who managed to counter Sammohanastra fired by Arjuna in Virat war.
7) BHAGDATTA.
He was the best elephant fighter of Dvapur yug. His elephant was not an ordinary one. It was stronger than atleast 10000 ordinary elephants as it had defeated Bhima and Ghatotkacha on 8th day and had almost killed Bhima who had the strength of 10000 elephants.
Fought against Arjuna for 8 days during his divvijaya yatra. In his youth he would be many tiers above. Despite being weakened by old age he suffered minimal defeats throughout his life and defeated the likes of Bhima, Satyaki, Abhimanyu and Ghatotkacha.
8) BHIMASENA.
He had defeated Kaurava warriors like Bhishma, Drona, Karna, Ashwathama and Bhagadatta. He also killed Duryodhana, Dushasana and 100 kaurava brothers of Duryodhana single handedly. Defeated Drona on 14th day and dominated Karna in archery duel four to five times and Duryodhana lost 20 of his brothers to save Karna. Bhima,’ s greatest feat in archeyr was defeating Karna on 17th day with his Vijaya bow. He stalemated Ashwathama on 12th day adn 16th day.
9) SATYAKI
Satyaki is an underrated warrior in Mahabharata and was a powerful warrior from Pandava side. He had defeated the likes of Bhishma, Dronacharya and Karna. On 14th day Satyaki defeated both Karna and Drona and killed many prominent warriors. He was one of the warriors who managed to survive 18 days of Kurukshetra war. Defetaed the rakshasa Alambusha and countered his illusions on 7th day.
10) GHATOTKACHA.
He too was a great warrior from Pandava side. He himself defeated the group attack of Drona, Ashwathama, Kripa, Bhurishrava in plain archery duel. Defeated Bhagadatta on 4th day who suffered minimal defeats. He was almost invincible on 14th night and Karna had to use vasavi shakti to kill him. Made Drona and Ashwathama retreat due to his deadly illusions.
During nightime he defeated and killed demons like Alambusha, Alambala and Alayudha who had even defeated Bhima. With his illusions Ghatotkacha would be above most of the warriors but in terms of archery skills he is below Bhima and Satyaki.