The Hardcore guild <HC Elite> has defeated Nefarian on Classic Era. This is the same guild that toppled Ragnaros during the Road to Rag event in early 2022. The Hardcore community has grown over time and there is currently a multiple week event taking place, known as the Hardcore Allstars. To learn more about the event, join the Hardcore Allstars Discord Server.
In this Hardcore run of Blackwing Lair there was a total of 0 deaths! Here is a link to the Warcraft Logs.