Here’s a really interesting visualization, as paraizord shared zone maps with highlighted locations of where Hardcore players had died and who killed them. This is based on data from the Deathlog addon, with 45,000 actual deaths logged in Classic. We also get to see what exactly killed them, as well as the level range of deaths by zone (you’d be surprised at the amount of sub-level 10 deaths).
There’s plenty of locations showcased in the reddit post below, and the highest number of deaths is mostly related to how many players chose which starting zone, and oh boy, there were a LOT of Night Elves not making it out of Teldrassil, and most of those were under level 10.
Other VERY deadly mobs include Voidwalker Minions from Durotar, Son of Arugal in Silverpine, Wendigo in Dun Morogh, Defias Trapper in Westfall and the MOST deadly mob in this overview: Kobold Miners from Elwynn.
The later zones are much more interesting, however, as there are fewer deaths and the players getting there are presumably more dedicates, so let’s take a look at the probably most classic Classic zone:
And here’s the full list with the 14 zones that were examined: