Throwing away all the contrived "Chosen One" nonsense none of them, even together could do anything to Nihlus. They die simply being near him. The Exile only beat Nihlus due to him being tricked by Kreia and starving. As well as his bond with Visas. The Exile literally had all the help possible. His (yes I'm saying "his" because I don't care what the Revan novel says about The Exile since it's trash) ability to beat Nihlus soley relied on Kreia's deception and his connection to Visas. Without them there's really nothing any force user could do outside of those circumstances. And his killing all life just by stepping foot on a planets surface trumps anything the names I mentioned in the title ever accomplished combined. Ironically their amazing connections to the Force is exactly why they would die.