In the Mahabharata, Karna has a one-point programme — he wants to defeat Arjuna. He is jealous of Arjuna’s prowess. So he never thinks about the costs of fighting Arjuna, and misleads Duryodhana too whenever he can, said V.S. Karunakarachariar, in a discourse. After Draupadi weds the Pandavas, all the kings who had come for the swayamvara depart. Duryodhana also had come for the swayamvara, but he had lost out to Arjuna. He is disappointed and angry.
Karna stirs up his anger further and says that now is the time to fight the Pandavas. He sets forth a number of arguments in his attempt to convince Duryodhana to take up arms against the Pandavas at once. For now, although King Drupada will fight on behalf of the Pandavas if they are threatened, there are no other strong supporters for the Pandavas. Once Krishna’s army arrives, their hands will be strengthened. So Karna advises Duryodhana that the time for subtle planning is past. The Kauravas must act swiftly, and vanquish the Pandavas, before they are prepared to meet the Kaurava attack. Karna abuses Drona and Bhishma, and says they have enjoyed the generosity of Duryodhana, but when it comes to giving advice to him, they are careful to ensure that the Pandavas are not harmed.
Karna does not care about the consequences of a fight. All he is interested in is the defeat of Arjuna. In the Mahabharata, we find Duryodhana always takes the wrong advice of people like Karna and Sakuni, and that proves his undoing.
During the Kurukshetra war, Karna and Jayadratha resolve that they will kill Arjuna’s son, and they succeed in killing young Abhimanyu by resort to trickery and deceit. Thus Karna’s jealousy of Arjuna leads to all round misery for everyone.