arjuna is no doubt greatest archer because he alone did not retreat from battle field karna retreated many times form arjuna in battle field
karna was even not able to defeat bheema and fled from him many times in
battle field and he defeated bheema by deciet karna even killed abhimanyu by deceit i agree that karna was generous but not a great warrior than Arjuna Arjuna is the Peerless Archer in Mahabharata.Arjuna,Drona,Bhishma are greatest warriors of mahabharata
there is no instance in mahabharata where arjuna was afraid of karna Arjuna singlehandedly defeated devas,gandharvas and nivathakavachas.he even fought with shiva and Lord Shiva himself said that
there was none equal to him.when jayadratha sought boon from lord Shiva
that he should defeat pandavas the lord shiva said that he himself is incapable of defeating arjuna then how can he give him the boon.
and some people have said that karna was asked by kunti not to use nagastra twice that is not true arjuna had greatest astra pashupata
but he did not rely on it for vistory he could have used it but he did not use it because he wanted to win victory by power of his arms but karna relied on shakti astra to kill arjuna
and again he used nagastra when he was not able to defeat arjuna by any astra or arrows.Karna was always jealous of arjuna
though he knew arjuna was his brotherhe still hated him and wanted to kill
him
some are saying that kuru army was not prepared to fight with arjuna at viratnagara so they lost this is not true they have come well
prepared and karna tried to defeat arjuna but he ran away from arjuna twice in battlefield and arjuna defeated all of them
karna was not even able to defeat abhimanyu and ghatotkatch what to be siad that he can defeat Arjuna
Arjuna is Greatest warrior
Jai Arjuna Jai Krishna