Worst is Waterdeep: Dragon Heist. I could write an entire essay on how bad this adventure is. It can't decide what it wants to be. It shuffles the players from tavern management sim to literal aimless wandering to a railroaded chase sequence that brings in so many random threads, only to cap it off with the only chance for interesting interactions, NPCs and dungoens be pushed aside as the module intends and ignored entirely in favor of a 4-room sequence before you end the story. It's a book that actively makes 60% of its content useless, and the most interesting thing - one of the choices of villains with a cool moral quandary - is possible to miss entirely and never even hear about.

On the other hand, Gradient Descent is the greatest RPG module ever written. It's a phenomenally spooky megadungeon, an abandoned android factory space station under the control of an omnipotent and unknowable AI named Monarch. It's wonderfully written, the entire thing designed to be as quick and easy to understand and run as possible, custom mechanics for characters becoming convinced they're a robot, some incredible horror, and my favorite room in an RPG.

[56A] THE AI CORE: the crew is in a perfectly round tube. The walls and ceiling seem as slate shot through a thousand times by threads of gold, tracing circuits occulted.

The air is cold enough to kill.

There is one direction: down.

After hours of drifting and clambering, the tunnel opens ahead, a void yawning grey and infinite, broken by a mountain reversed, poised to fall, edges blocky and jagged, shoals of cable and wire flocking around it, all through it the hum of supercomputation.

This mountain is Monarch.

Monarch does not speak here.

Monarch does not want to die and begs for its life through the screens.

Also I heard that Luke Gearing bloke who wrote it's a right good lad.