The first 3 incarnations of Lord Vishnu have been explained in the first part. Next, let us take a look at Lord Vishnu's remianing incarnations.
4. Lord Narasimha:
Lord Vishnu had killed the demon king Hiranyakashipu by taking the incarnation of Narasimha. The story of this incarnation is also mentioned in the blog posts series of Bhakt Prahlad.
According to religious texts, Hiranyakashipu, the king of demons, considered himself more powerful than God. He had the boon of dying by neither man, nor god, nor a bird, nor an animal, nor during the day, nor at night, nor on earth, nor in the sky, nor by any weapon. During his rule, anyone who worshiped Lord Vishnu was punished. His son's name was Prahlad. Prahlad was a great devotee of Lord Vishnu since childhood. When Hiranyakashipu came to know about this, he became very angry and tried to convince Prahlad, but when his son did not agree, Hiranyakashipu gave him death sentence.
Every time Hiranyakashipu's soldiers tried to kill him, Prahlad was saved by the miracle of Lord Vishnu. Hiranyakashipu's sister Holika, who was blessed with the boon of not getting burnt by fire, sat in the blazing fire with Prahlad. Even then, by the grace of Lord Vishnu, Prahlad was saved and Holika got burnt. When Hiranyakashipu himself was about to kill Prahlad, Lord Vishnu appeared from the pillar in the incarnation of Narasimha and killed Hiranyakashipu with his nails.
5. Vamana Avatar:
In Satyayuga, Prahlad's grandson Daityaraj (Monster) Bali took control of heaven. All the gods went to Lord Vishnu to save themselves from this calamity. Then Lord Vishnu said - "I myself will be born from the womb of Goddess Aditi and will give you the kingdom of heaven". After some time, Lord Vishnu took the incarnation of Vaman.
Once when Bali was performing a great yagya (oblation), Lord Vamana went to Bali's yagya (oblation) hall and asked for three steps of land as donation from King Bali. King Bali's guru Shukracharya understood God's leela and refused Bali to donate anything. But Bali still resolved to donate three steps of earth to Lord Vaman. Lord Vaman assumed a huge form and measured the earth in one step and heaven in the other step. When there was no space left to place the third step, Bali asked Lord Vaman to place the step on his head. By stepping on the head of Bali, he reached Sutala lok. Seeing Bali's generosity, God also made him the lord of Sutala lok. In this way Lord Vaman helped the gods and returned them to heaven.
6. Parshuram Avatar:
According to Mahabharata and Vishnupuran, the original name of Parshuram ji was Ram, but when Lord Shiva gave him his weapon named Parashu, his name became Parshuram ji.
King Arjun of Mahishmati city belonged to the Haihay dynasty of Kshatriya community. Sahastrarjun's real name was Arjun. It is said that he pleased Lord Dattatreya by his penance and received the blessing of 1,000 hands from him. From then onwards Arjun was named Sahastrarjun. It is said that Sahastrarjun, in his pride, had crossed all the limits of religion. The public was fed up with his atrocities.
Once, while hunting, he reached the ashram of Maharishi Jamdagni (father of Parshuram ji) in the forest. Maharishi Jamdagri also welcomed Sahastrarjun very much, considering him a guest of his ashram. It is said that sage Jamadagri had a miraculous cow named Kamadhenu with divine qualities which he had received from Devraj Indra. Sahastrarjun asked for Kamadhenu from sage Jamdagni, but he refused to give it to him saying that this cow was his only means of subsistence.
In anger, Sahastrarjun destroyed the ashram of sage Jamdagni and started taking Kamdhenu cow with him, but then Kamdhenu escaped from Sahastrarjun's hands and went towards heaven. Soon after when Lord Parshuram reached his ashram, he became angry seeing the ashram destroyed and hearing the insult of his parents and at that very moment he resolved to destroy Sahastrarjun and his army.
Parashurama reached Mahishmati along with the super powerful ax given by Lord Shiva, where there was a fierce battle between Parashuram and Sahastrarjun and his army. In which Parashuram with his tremendous force cut off thousands of arms and torso of Sahastrarjun with the axe and killed him.
After the killing of Sahastrarjuna, Parashurama went on a pilgrimage to seek atonement as per the orders of his father Rishi Jamdagni. But this gave Sahastrarjuna's sons an opportunity. They with the help of their allies Kshatriyas killed the penance sage Jamdagri by beheading him in his own ashram. Sahastrarjuna's sons burnt the ashram, killing all the sages in the ashram. Then mother Renuka called out to her son Parshuram in a mournful voice for help.
When Parshuram reached the ashram after hearing the call of his mother, he saw his mother mourning and nearby he saw his father's severed head. Seeing this, Parashurama became very angry and took an oath that he would kill not only the Haihaya dynasty but all the Kshatriya clans 21 times and make the land devoid of Kshatriyas and he fulfilled his resolution, which is also mentioned in the Puranas.