Long-running franchises that never recovered from one entry?

This might be too close to recent threads but ima do it anyways.

Green Lantern had nowhere to go but up in 2010. Geoff John's revitalization of the lore with the Emotional Spectrum had resulted in a plethora of mainstays and the Blackest Night event. A movie was coming out from the director of Goldeneye and Casino Royale, and it was going to launch a DC cinematic universe, how logical since GLs can pop up anywhere. GL the Animated Series came out and was praised. Green Lantern was cool.

And then the movie bombed.

Since then, it's been rough times for GL as DC took its frustration with its failure out on the franchise. Hal Jordan was the "uncool guy" in the Justice League twice in animated outings and GLs got the short end in the DCEU (which was fortuitous in retrospect), GLs went back to being killed regularly in the comics, and a bunch of nonsensical new GLs were introduced as the creators flailed with the direction going forward.

And Nathion Fillion is looking great...as the comic relief in Superman, as much as I love Guy Gardner.

What other franchises suffered severe setbacks they haven't recovered from, from just one tainted entry? Must be longrunners.