When Madara used the Izanagi before Hashirama killed him, he survived at the cost of one of his eyes. But when he activated his Rinnegan decades later, his eye was restored.
So if you have Rinnegan and you perform Izanagi/Izanami, does that mean that there are no drawbacks? If that's true, then that would be invincible, since someone like Madara can use it endlessly and never lose in a battle.