In the ultimate Vaishnavite purana, Vishnu-purana - Narasimha hardly exists. Hiranykashipu repents and Vishnu gives him boons. It is parenthetically mentioned that he was killed by Narasimha, but the "near-invincibility" boon is absent.
Vaishnavite partisans claim to see Narasimha in Rig Veda
I WILL declare the mighty deeds of Viṣṇu, of him who measured out the earthly regions, Who propped the highest place of congregation, thrice setting down his footstep, widely striding. For this his mighty deed is Viṣṇu lauded, like some wild beast, dread, prowling, mountain-roaming; He within whose three wide-extended paces all living creatures have their habitation.
Nothing associates lions with mountains. Whatever this means, it is pure fancy to say that Narasimha appears in Rig Veda.