Parashurama - Maharshis of Ancient India

Parashurama, considered to be the sixth incarnation of Lord Vishnu, was born in the Bhrigu clan to Jamadagni and Renuka. Born as Rama, he came to be known as Parashurama, 'Parashu' meaning 'axe'. This is because he destroyed the Kshatriya clan with his divine axe in revenge for the death of his father at the hands of a kshathriya king's sons. He received a number of divine weapons after performing tapas to Lord Shankara.
He was obliged to kill his own mother and brothers in deference to his father's wishes but using the boon that he received from his father, he brought all of them back to life. He went round the world 21 times killing all the bad kshatriya kings and princes but repented the bloodshed he had caused. So he went deep into the forests to perform tapas. He gifted away all the land that he had conquered to sage Kashyapa and lived a solitary life in "Shoopanaraka'.
 Parashurama challenged Lord Rama to use MahaVishnu's bow and was shocked that the latter could do it with great ease. He then realized that Rama was none other than Lord Vishnu himself. So he went round him once and then proceeded to Mt. Mahendra for tapas.  Drona sought him as a guru which he obliged but with Karna, it was a different story. When he came to know that Karna had not revealed his lineage, he cursed him and blessed him as well.
He fought a long drawn war with Bhisma, one of his best students, in an attempt to make him accept Amba. All the devas had to intervene and dissuade him from wielding the Praswapanastra against Bhisma. He was not only impressed with Bhisma's prowess but acknowledged it openly as well. It was only when Mother Ganga asked to stop the fight that he relented. Parashurama, the great tapasvi, the best among brahmanas, most feared and respected, saved the world from evil forces and established the rule of law in it.