Lucifer had to follow Izanami's rules if he wished to deal with her. If he wanted to destroy her though, I'm sure he could just wipe out her realm with her in it. The first time he entered her realm, it was to retrieve his wings and the second time was to retrieve a portion of the letter of passage. Wiping out her realm wouldn't have helped him to achieve his goals.
I doubt the Vishanti could affect his powers in any way without his permission. If the Vishanti are a bit more powerful than Galactus, they're going to lose. If they're more on a level of Eternity, this could be a great fight.