I have always liked Karna's character the most. Great disciple, Skilled archer, most reliable friend. What more..!! But yet, I pity him too. Firstly his mother abandoned him for a mistake committed by her. Secondly for being rejected by Draupadi during her swayamvar saying that, she didn't want to marry a charioteer's son. Thirdly his fate. Still, he faced all with dignity and won the admiration of many but for these 3 curses which led to his downfall in the battle field of Kurukshetra.
One
Karna admired Dhrona and asked his permission to make him his disciple. But Dhrona refused, giving caste as the reason. He then approached Parashuram, the guru of great sages like Dhrona himself and Bhishm. Parashuram accepted him inspite of his low status. Karna was a great disciple and was mastering the skills of archery when Indra realised that these skills might hinder the progress of his son Arjuna. One day while the sage was resting on Karna's lap, Indra took the form of a bee and stung karna. He bored into his knee deeper and deeper. He tried his best to withstand the pain so that his guru wouldn't be disturbed. When the sage woke up he was astonished to see blood flowing and cursed him saying "Such tolerance is present only in a true Kshatriya. You have lied to me to learn archery from me. May you forget the holy incantation's when you need to use them. "
Two
While Karna was traveling on a chariot, he sees a lion near a calf in the fence of a house Fearing that lion might eat the calf, he aims and kills the lion. This was another wicked trick of Indra who made the mother cow look like a lion to put Karna into trouble. The owner of the cow, a brahmin curses Karna "This cow was every thing to me and my family and you have made me helpless now. In the very same way, you will be killed when you are defenseless."
Three
Once Karna's horses make a loud noise and small girl holding ghee in a vessel spills it out of fear. He offers to buy her new ghee but the little girl is stubborn and wants the same old ghee which is now mixed with mud/earth. He however takes a fistful of earth and squeezes it till he gets some ghee out of it. Mother Earth unable to bear the pain, punishes him saying "For a little girl, you have caused so much pain to me. When you are about to kill your enemy your chariot will sink into earth".
Thus bound by these curses he was killed by Arjuna, but still remains one of the most celebrated persons of Hindu mythology.
