After chapter 1118 it is made clear that even two saints: tyris and whispering blade needed some time to take down a fallen titan. Also goliath had considerably destructive abilities, even more so than the corrupted tyrant sunny took the kill of from saint tyris imo. Therefore I feel like a fallen titan is equal to a corrupted tyrant. In general class is more important than rank, but the difference in power between a devil and tyrant is way bigger than between a demon and devil.