After the death of Ghatotkacha, bhagavAn makes this curious statement,

gANDIvamudyamya bhavAMshchakraM chAhaM sudarshanam . na shaktau svo raNe jetuM tathAyuktaM nararShabham

He says neither the gANDIva nor the Sudarshana can overcome KarNa if he had the armor and earrings+

Sudarshan & bhagavAn both have unsurpassed power. Then why does he say that?

Note that he refers to Arjuna's bow and his Chakra by name. This is quite redundant because Arjuna would know the names anyway. So the key lies in the reference to the names. Look the preceding shlokas+

diShTyA.apanItakavacho diShTyA.apahR^itakuNDalaH . diShTyA sA vyaMsitA shaktiramoghA.asya ghaTotkache

[By fortune, ie, my grace, his kavacha was taken away, by that fortune, his kuNDala was taken away & his shakti astra which is never futile, was confounded by ghatotkacha]+

Here, “diShti” means bhagavad anugraha in the form of good fortune.

Acharyas have pointed out that there is no such thing as “luck” in shAstra, wherever “aho bhAgya” or something like that is mentioned, it refers to bhagavAn’s will in the form of grace only+

gANDIvamudyamya bhavAMshchakraM chAhaM sudarshanam . na shaktau svo raNe jetuM tathAyuktaM nararShabham

 [You with your gANDIva and me with my sudarShana chakra, are not capable of defeating him in battle if that bull among men had his kavacha and kuNDala.]

Explanation+

vedAnta desikan explains bhagavad sankalpa or sva-sankalpa, is “svAdhikAram”  and this is called “darshanam”.

Thus, “sudarshanam” means his auspicious will – the “su” implies uniquely auspicious nature of that will+

“sva-sankalpa kalA-kalpair-Aayudhair-AayudhEsvara:” – The Chakra is merely an embodiment of his will and the subweapons held by Sudarshana are “fragments” of that will+

The chakra is basically his will in action. So if karNa had the kavacha and kuNDala, then by his will to ensure the power of those objects is sustained, it cannot conquer him.

That will (darshana) has “su” prefixed to it to show he is not arbitrary or prejudiced in his will+

In contrast, “gANDIva” is so called as it is the chastiser of foes. Even that bow would not be able to chastise karNa, the most dreaded foe.

So, while Arjuna would not be strong enough, bhagavAn did not have the will to destroy the kavacha and kuNDala to uphold their power+

Though his will was to sustain the power of the articles karNa wore, his will also took the form of grace to remove them from KarNa, as mentioned previously. Thus, he acted impartially, but with special affection to his devotees+

The obvious inner meaning to all this is that karNa is lust. The golden armor is the hankerings, the incessant contemplations of sense objects as “gold” signifies attractiveness. “kuNDala” means any fetter or rope as well, and denotes attachment+

So long as the jIva has attachment & hankerings, bhagavad anugraha is obstructed & his sankalpa takes the form of sustaining them due to that being the desire of the jIva driven by karmas.

The gANDIva which signifies the meditation of the jIva on the self cannot destroy it too+

Thus, lot of depth in this statement of bhagavAn. The very fact he named his chakra and the bow of Arjuna in talking about this shows this is the implied meaning//