Worst one in history: Myth II.
Whatever hard disk it was installed on, it would wipe clean upon install.
Dems were sum recalls.
I’d have to say a pretty bad one was Black Mesa.
I downloaded it and installed it, and all it gave me was this stupid virus 
There was a part in Uncharted 2 where I had to have Elaina’s help to open a door but she stayed in cover like there were still enemies around even though they were all dead. I had to reload an earlier save and kill the enemies all again to get past it.
Hell, the chapter “Keep Moving” never worked right because the AI kept falling behind on hitting their cues, so a door that was supposed to be open wouldn’t be open and I’d get gunned down. Uncharted 2 was damn fun but had quite a few bugs ><
In RollerCoaster Tycoon 3, “Peeps” can’t seem to pathfind to a ride unless it’s right in front of the FUCKING ENTRANCE
It’s really that bad? RCT2 apparently had better AI? That’s sad…
The icing on the rage cake was that after applying every patch, you had to start over from the beginning. in its first 2 weeks, there were over 4 patches that all either wiped your saves or rendered them unusable.
-Kawai Tei-