Hiranyakashipu was the demon who was killed by the Narasimha Avatar of Bhagavan Vishnu. The story of Hiranyakashipu begins with Sage Sanaka cursing the doorkeepers of Vishnu, Jaya and Vijaya. The doorkeepers once did not give entry to Sage Sanaka to Vaikunta, the abode of Vishnu. Jaya was born as demon Hiranyaksha and Vijaya was born as demon Hiranyakashipu as a result of the curse.
Vishnu appeared as Varaha to annihilate Hiranyaksha.
To avenge the death of his brother, Hiranyakashipu undertook severe penance and secured several boons from Lord Brahma. The most important boon was that he could not be killed by man or beast, or by a weapon, during day or night, on the earth or in the sky, inside a house or outside.
After receiving the boon, he conquered the three worlds and prevented all forms of Vishnu worship including utterance of the name of Vishnu.
But his youngest son Prahlada had heard about the story of Vishnu when he was in the womb of Kayadhu.
Hiranyakashipu tried all methods to stop his son from worshipping Vishnu. When he failed in his attempts, he ordered his son to be executed. But all methods to kill Prahlada turned futile.
One day an angry Hiranyakashipu asked his son to show where Vishnu was. Prahlada replied calmly that He is everywhere. When asked if Vishnu was there in a pillar, Prahlada replied in the affirmative.
Hiranyakashipu then banged the pillar with his mace, whereupon Vishnu appeared in the form of Narasimha and annihilated him.