Why is The Tomb of Horrors so infamous?

Well you see, the very first campaigns of DnD were created to be fun adventures but then, Gary Gygax, one of the co-creators of DnD wanted to spiced things up by making a campaign that would be 'challenging' for the players. And by challenging, I mean one mistake could kill your party in one fell swoop. Seriously, Gygax had literaly say that on this campaing, the Dungeon Master, instead of guiding the players, must work to actively kill the players.

What make Tomb of Horror so special is that it had so little monster encounters. It was monstly focused on deadly traps. Lot of traps. Pitfalls in nonsensical places. Paths that led to instand deaths without any hints. Riddles super hard to solve. Portals that teleport you back at the 'start' of the dungeon completly naked. (No, this is not a joke.). Even fake final boss and fake treasure. And of course, the iconic Face with the Sphere of Annilhation that ended whole party in the must dumb and comical way I can think of.

Basically, it's infamous because instead of being fun, this campaing cause a lot of players to rage quit. A lot. But it's ironicaly why that, even today, this old campaing as reach the status of legend and has still a soft spot in the Dungeon and Dragons community.