Karna....

Growning up Karna was an idol to me. He still is a great character and gets a lot of respect from me.
One view of Karna can be that he may be your self sacrificing kind of guy, who knows his limitations, but tries to achieve personal fame through his deeds and actions. He might be selfish in this aspect. His aim was for eternal fame. :) (Atleast that is what I think, my personal opinion)
He is simply a very interesting Psychological study.

Karna did not suffer much different than a lot of other people either in his time or later times. That is not an excuse provided by him either. People assume it to be his excuse. That is all.
Karna knows he is not on the side of Dharma but still elects to honor his friendship with Suyodhana rather than jump the ship when it was sinking. He is honored and respected because of his decision to continue with Duryodhana. He elects to be a normal human being by giving up a lot of his god given advantages.

You also see that his conduct on the battlefield is beyond reproach. The moment he becomes the commander, he follows the dharma correctly and does not continue war after sunset. If you point out Abhibanyu’s death, karna attacks him in the beginning and breaks his bow and then just watches the killing. You also need to understand that he was under the command of Drona and had to follow orders.

Do you think Karna does not know he would die in the battle? He knows that his last fight with Arjuna would be the most crucial moment in his life. And he knows that his perceptor has cursed him to lose all knowledge of weaponry at the most crucial moment in his life. Karna, assuming that he is a person of normal intelligence atleast, can equate both.

From Pradip Bhattacharya's work:

For Karna, the fact of his inferior birth is a poison eating into his soul and impelling him to acts of incredible prowess. He conquers single-handed for Duryodhana all the territories that the four Pandavas had won for Yud’s Rajasuya Yajna. Once he even worsted the mighty Jarasandha, who gifted him the town of Malini in appreciation. For the same reason he took the vow of never refusing a mendicant, and thereby knowingly deprived himself of his invulnerability and his benefactor Duryodhana of sure victory.
It is karna’s inflexible determination to stick to his word, whatever the consequences, which leads to doom. It is of him that Yudhishthira is the most apprehensive. Krishna sets much store by Karna, Knowing that if he stands aside Duryodhana would not dare go to war. On more than one occasion Krishna tries to persuade Karna to join the Pandavas.
Unfortunately, Vyasa does not tell us of the inner workings of Karna’s mind and heart.
Karna, is a man divided against himself, yet undoubtedly noble in his silence about his mother’s secret and wise in his judgement. For, he tells Krishna not to reveal the secret to Yudhishthira who will invariably offer the kingdom to him and he will inexorably hand it over to Duryodhana. All his tremendous power has throughout been put in the service of adharma because of his profound sense of a lacerated ego.
Here is a hero who knows, that he is on the side of wrong, but is a slave of his word and will not shift to support what he knows to be the right. His greatness as a man shines radiantly in the fact that while he knows that he is battling his blood brothers, and is promise-bound not to slay them, they are all eager to kill this charioteer’s son! His slicing off the skin-armour and flesh earrings is an external symbol of the inner splitting-in-two of his very psyche. One part of him knows that Duryodhana’s plans are evil. This part in Karna is all that is admirable in a human being.