Lord Parashuram can be understood as a partial incarnation of Lord Vishnu.
Parshuram who is well-versed with the four Vedas and sports the bow and arrow upon His back (that is the one who has the radiance of both the Brahman and the Kshatriya) will destroy evildoers either with a curse or with an arrow.
When fighting, mere use of weapons is insufficient for a seeker. He should have the potential to curse in conjunction with the former. Shri Parshuram single-handedly eliminated the Kshatriyas from the earth, circumambulating it twenty-one times. What exactly does this mean? He destroyed the evil Kshatriyas. If He were to completely destroy all the Kshatriyas on the earth even once then not a single Kshatriya would have survived for the second round. However He slew only the evil Kshatriyas. Let us all attempt to destroy the evildoers atleast once.
Bhagwan Parshuram, the sixth Incarnation of Vishnu, is the son of Jamadagni and Renuka. Parshu means axe, hence His name literally means Ram with the axe. He received an axe after undertaking a terrible penance to please Lord Shiva, from whom He learned the methods of warfare and other skills. Even though He was born as a Brahmin, He had Kshatriya (warrior) traits in terms of aggression, warfare and valour. Hence He is said to be a ‘Brahma-Kshatriya’ and one who possesses both, Brahmatej and Kshatratej.
He killed the entire army and King Kartavirya Sahasrarjuna, who took away the magical cow (Kamadhenu) forcibly, that belonged to His father Jamadagni. In revenge, the King’s sons killed Jamadagni in Parshuram’s absence. Furious at their unrighteous act, He killed all sons of the King and also went on killing all corrupt Haihaya Kings and warriors on the earth 21 times. He then conducted the Ashvamedha Yadnya (sacrifice), done only by sovereign Kings and gave the entire land He owned to priests who performed the sacrifice.
He is a Chiranjeevi (Immortal) who fought the advancing ocean back, thus saving the lands of Konkan and Malabar (Maharashtra – Karnataka – Kerala coastline). The coastal area of Kerala state along with the Konkan region, i.e. coastal Maharashtra and Karnataka, is known as ParshuramKshetra (area).
He has been a Guru to Bhishma, Dronacharya and later also to Karna. He taught Karna the extremely powerful Brahmastra (a celestial weapon). But He also cursed that the knowledge would be useless to Karna, predicting much in advance that Karna will join the unrighteous Duryodhana in the Kurukshetra war. Such was His love for Righteousness.
अग्रत: चतुरो वेदा: पृष्ठत: सशरं धनु: ।
इदं ब्राह्मं इदं क्षात्रं शापादपि शरादपि ।।
In the Ramayana, Parashurama had given the bow of Shiva to the father of princess Sita for her swayamvar. As a test of worthiness, suitors were asked to lift and string the mythic weapon. None were successful until Rama, but in the process of being strung, the bow snapped in half. This produced a tremendous noise that reached the ears of Parashurama as he meditated atop the Mahendra Mountains.
When he then turned to confront Rama, Parashurama was unable to lift his axe. He was held back by the brilliance of Lord Ram. When the warrior-sage realized he was looking at his own subsequent reincarnation, his own bow flew to Rama along with the essence of Vishnu, and thus the seventh avatar was fully realized.
Karna was half brother to the pandavas and son of Surya, but raised by a low caste charioteer. Karna came to Parashurama after being rejected by Drona due to his perceived caste. Karna lied and said he was Brahmin, and so Parashurama accepted him as his student, giving him knowledge of the powerful Brahmastra weapon.
One day, Parashurama was sleeping with his head resting on the lap of Karna and a scorpion crawled up the leg of the student and bit his thigh. In spite of the pain, Karna neither flinched nor cried so his guru could rest. Warm blood, however, trickled down his leg, waking Parashurama. Convinced that only a Kshatriya could have borne such pain in silence, Parashurama realized the lie of Karna, and cursed his student that his knowledge of the Brahmastra would fail him when it was most crucial.
Years later, during the Kurukshetra war, Karna had a dream in which he envisioned his guru and asked him to take back the curse he had given years back. Parashurama revealed that he had known all along Karna was a Kshatriya, but because he was a worthy student Parashurama had instructed him regardless. The avatar explained to Karna that the Brahmastra had to fail him when he needed it most. If he killed Arjuna, Duryodhana would be king instead of Yudhishthira, and chaos would ensue. Parashurama asked Karna to accept his curse and die at the hands of Arjuna, that the world might live in peace.