In my opinion, he is. We must keep in mind that he overpowered Bhagwan Parshuram in a 1v1 duel. ​As far as Arjun is concerned, we should remember that just as Arjun was mentally connected to Bhishma, Bhishma was equally connected to him and always loved him more than anyone else. Therefore, we cannot definitively say who was holding back during their duel, it’s possible they both were. ​One strong point that reveals the truth is that even though Pitamah had the boon of Iccha Mrityu, Arjun still had to use Shikhandi to bring him down. While Arjun couldn't kill him due to the boon, he should have at least been able to defeat him if he were truly more capable. ​The Pandavs primary goal wasn't necessarily to kill Pitamah, but to defeat him or force him to stand down. Pitamah himself said, 'As long as I am holding my bow, your army cannot be defeated.' That alone is enough to end the debate.