Here is a list of Insanely powerful warriors excluding Shri Krishna and Balram.
ABHIMANYU
Abhimanyu was the son of Arjuna. He heard about the strategies to enter into the Chakra Vyuha when he was in his mother’s womb. Yudhisthira instructed, Abhimanyu to break the Chakra vyuha formation. He knew the secret of entering the Chakra vyuh formation, but did not know how to exit it. He slew tens of thousands of warriors. He also killed Dhuryodhana’s son. Duryodana ordered his men to attack Abhimanyu all at once. He fought but was surrounded and killed by many warriors in a combined attack.
BHISHMA
Bhishma is the grandfather of both the Pandavas and the Kauravas. The Pandavas, unable to withstand Bhishma’s prowess, decided to put Shikhandi, who had been a woman in a prior life in front of Bhishma, as Bhishma has taken a vow not to attack a woman, Arjuna positioned himself behind Shikhandi, protecting himself from Bhishma’s attack. Soon, the great warrior fell from his chariot.
JARASANDH
Extremely powerful. He was the mightiest king when he died. He had the biggest army of any king. He had imprisoned 86 kings in his prison. He was able to attack Krishna 17 times and every time he came with over an akshahoni army. That is insanely high numbers. At the end Krishna was forced to leave mathura and shift to Dwarka to live peacefully.
PRADYUMNA
Pradyumna, was the eldest son of Sri Krishna and Rukmani, he was the re-incarnation of Kamdeva, taught magic and illusion by Rati herself, he was the mightiest warrior as described in Mahabharata.
BARBARIK
He was the son of Ghatotkacha, grandson of Bheem. The story of Barbarik is found in Skanda Puran. According to that story , Barbarik had three arrows. First one to mark the target, second one to lock the target and third one to run away from the target. But the problem was that he would fight for the weaker side. So Sri Krishna asked him what would he do, if his opponents’ sides strength got reduced.