The third console curse: Which was the biggest stumble?

[Wman1996]

All did some damage, of course.
Least damage: Nintendo 64. Yes, it was outsold globally by the PS1 by a little over 3 to 1. So, in that way it fumbled the generation for Nintendo and led to an even more severe gap in hardware sales in the sixth generation. It was profitable, and games like Super Mario 64, Zelda: OOT, GoldenEye 007, Super Smash Bros. and Animal Forest (JP only) and others changed the industry forever. Also, innovations like 4-players with no multi-tap needed, a Rumble Pak, and an analog stick.
From there, I can hardly pick between PS3 and Xbox One. PS3 lost Sony billions of dollars and required massive course correction both for PS3 itself and the planning of PS4. Xbox One had epic fails during its unveiling, many of which were course-corrected before launch and after launch. Xbox One ended up delivering some great experiences by moving away from Kinect and the "VCR" model, Game Pass, One X, etc. Still, Xbox One is to blame for many of the issues they still have with Series X/S which is now tracking below Xbox One largely because a new console is already confirmed to be in development.
Sega Saturn is the biggest failure. The add-ons of the Mega Drive (CD and 32X) in addition to the Saturn itself made Dreamcast pretty much dead on arrival even with its initial and short success. Dreamcast would've had to be a hit to reverse Sega's dying console business.