King Kaartaveerya-arjuna and his army visited Jamadagni, who fed his guest and the whole army with his divine cow; the king demanded the cow and Jamadagni refused because he needed the cow for his religious ceremonies. King Kaartaveerya-arjuna sent his soldiers to take he cow and Parashurama killed the entire army and the king with his axe. In return, the princes beheaded Jamadagni. In revenge, Parasurama killed the entire clan of Kaartaveerya-arjuna, thus conquering the entire earth, which he gave to Kasyapa.
According to one legend, the story goes on that Parashurama was struck by remorse at his wanton killings, and offered penance on a mountain top. The sea god Varuna responded, and offered him land equal to the distance he could throw his axe. Parasurama threw his axe from Gokarnam and it fell at Kanyakumari. As promised the sea gave way to land, thus giving rise to Kerala.
Parashurama also went to visit Shiva once but the way was blocked by Ganesha. Parashurama threw the axe at him and Ganesha, knowing it had been given to him by Shiva, allowed it cut off one of his tusks.
In the Ramayana, Parashurama came to the betrothal ceremony of the seventh avatar, Rama, to the princess Sita. As a test of worthiness the suitors were required to lift and string the bow of Shiva, given to the king Janaka by Parshurama. Rama successfully strung the bow, but in the process it broke in two, producing a tremendous noise that reached the ears of Parashurama. He arrived at the wedding and exchanged angry words with Lakshman, the brother of Rama, before being mollified by Rama.
In the Mahabharata, Parashurama was the instructor of the warrior Karna, born to a Kshatriya mother but raised as the son of a charioteer (a Shudra). Karna came to Parashurama after being rejected from the school of the teacher Drona, who taught the five Pandava and one hundred Kaurava princes. Parashurama agreed to teach Karna, believing him to be of Brahmin birth, and gave him the knowledge of the extremely powerful Brahmastra weapon. But one day while Parashurama was sleeping with his head resting on Karna's leg, an insect crawled up and bit Karna. He, not wishing to wake his teacher, did not move or cry out, but the flow of his blood eventually awakened Parashurama. Convinced that only a Kshatriya could have born such pain in silence and that Karna had therefore lied in order to receive instruction, he cursed Karna that his knowledge of the Brahmastra would fail him when he needed it most.