PHYSICAL STRENGTH OF ARJUNA

Arjuna’s strength feats.

Dragged Lord Shiva and struck him:

Narr:-  'Alas, my arrows are all exhausted. What shall I shoot now from my bow? Who is this person that swalloweth my arrows? Slaying him with the end of my bow, as elephants are killed with lances, I shall send him to the domains of the mace-bearing Yama.' The illustrious Arjuna then, taking up his bow and dragging the Kirata with his bow-string, struck him some fierce blows that descended like thunderbolts. Vana Parva: Kairata Parva: Section XXXIX

Seized Lord Krishna and stopped him from moving: 

Narr:- Meanwhile, the mighty-armed Partha. quickly following Kesava behind, seized him by encircling him with his two arms. That best of male beings, viz., Krishna, of eyes like lotus petals, seized by Partha, still proceeded with great speed, bearing the latter away with him. The mighty Partha, that slayer of hostile heroes, however, forcibly catching hold of his legs, stopped Hrishikesa with great difficulty at the tenth step. Bhishma Parva: Bhagavat-Gita Parva: Section CVII

Arjuna defeated 4 crocodile with his bare hands.

Narr:- "Vaisampayana continued, 'Hearing these words of the ascetics, that foremost of men endued with mighty arms, though dissuaded by them went to behold those waters. Arrived at the excellent sacred water called Saubhadra after a great Rishi, the brave scorcher of all foes suddenly plunged into it to have a bath. As soon as that tiger among men had plunged into the water a great crocodile (that was in it) seized him by the leg. But the strong-armed Dhananjaya the son of Kunti, that foremost of all men endued with might, seized that struggling ranger of the water and dragged it forcibly to the shore. But dragged by the renowned Arjuna to the land, that crocodile became (transformed into) a beautiful damsel bedecked with ornament. 

http://sacred-texts.com/hin/m01/m01219.htm

According to bori, Arjuna threw down all Samsaptakas who had climbed on his chariot.

Rishi Maitreya accepted that Arjuna had power of 10000 elephant.

Narr:-  'O mighty-armed Duryodhana, O best of all eloquent men, O illustrious one, give heed unto the words I utter for my good! O king, seek not to quarrel with the Pandavas! And, O bull among men, compass thou thy own good as also of the Pandavas, of the Kurus and of the world! All those tigers among men are heroes of high prowess in war, gifted with the strength of ten thousand elephants, with bodies hard as the thunderbolt, holding fast by their promises, and proud of their manliness!

http://www.sacred-texts.com/hin/m03/m03010.htm

NOTE:-  All those tigers among men means All pandavas

CONCLUSION: Arjuna wins. Someone who can compete with Lord Krishna and Lord Shiva in terms of strength will win against anyone below them (like Karna). HANDS DOWN! Physically Arjuna > Karna. Arjuna fought the gods of our universe (Shiva & Arjuna).