Karna and It's not even Close
Karna when giving away his Armor, Peeled his own skin with a Radiant Dart. He literally rips his own skin and shown no sign of Pain or difficulty, He was literally Smiling:
Vaisampayana continued, "Thereupon, O king, taking the blazing dart, Karna began to peel off his natural mail. And beholding Karna cutting his own body, the entire host of celestials and men and Danavas set up a leonine roar. And Karna betrayed no contortions of face while peeling his mail. And beholding that hero among men thus cutting his body with an weapon, smiling ever and anon, celestial kettle-drums began to be played upon and celestial flowers began to be showered on him. And Karna cutting off the excellent mail from his person, gave it to Vasava, still dripping. And cutting off his ear-rings also from off his ears, he made them over to Indra.
- Gods, humans, and Rakshas watched this extraordinary act and roared in amazement and admiration.
- The heavens celebrated his Act and the gods honoured him by playing divine instruments and showers of flowers.
What can be more glorious and daring than this? Other characters would have died, cried or gotten Unconscious on the spot with such Brutual Pain, Many wouldn't have even dared to cut their own body.
This is not the only act, Which shows Karna endurance. When Prashuram was resting on Karna's lap, A Celestial-Demonic insect started piercing Karna:
White his preceptor was thus sleeping (with head) on his lap, a frightful worm, whose bite was very painful and which subsisted on phlegm and fat and flesh and blood, approached the presence of Karna. That blood-sucking worm, approaching Karna's thigh, began to pierce it. Through fear of (awaking) his preceptor, Karna became unable to either throw away or kill that worm. Though his limb was bored through by that worm, O Bharata, the son of Surya, lest his preceptor should awake, suffered it to do its pleasure. Though the pain was intolerable, Karna bore it with heroic patience, and continued to hold Bhrigu's son on his lap, without quivering in the least and without manifesting any sign of pain.
Karna endured that Pain without moving an inch. He silently suffered and bore the intolerable Pain without showing any signs of it.
This is enough to say that When it comes to Endurance, Karna stands at the Top. Neither Pandavs nor Kauravas or anyone else can surpass Karna interms of Endurance.
Show some respect to the Fallen Angel of Sun~
My Answer is based on KMG Mahabharat,