Slander and Avici Hell? I read about how instead of believing if slander is done then that person will goto Avicii Hell. I don’t see this discussed much when researching Buddhism, it seems mainly mentioned by Nichiren? 

Does anyone have more information about what this means? What is everyone’s thoughts on this? Why isn’t there more information on something so big?
For bikkhus, You can look at the vinaya, Monks’ Pācittiya 3,
https://suttacentral.net/pli-tv-pvr1.2/en/horner-brahmali

the buddha says that you go to hell when you slander the buddha or the noble ones, like here https://suttacentral.net/sn6.9/en/sujato

https://suttacentral.net/t211.30/en/beal

but for slander of a puthujjana by another puthujjana, that's seems to be the usual harsh speech, so no explicit direct destination.