For me Just Cause 4 is the worst one for too many reasons to list. Also, I'm still not sure about Kingdom Come: Deliverance 2, but that could have a lot to do with not being ready to play a middle aged, yolked Henry lol

(Edit: Oh and Sniper Elite 6 seems like a contender too. Although SE5 was very poorly received at the beginning until they fixed the issues and then it turned into one of the most awesome games ever so who knows...)

Prince of Persia. First two were good, though a glitch toward the end of the second one kept me from finishing it.

The third one was an abomination. Completely different tone and vibe, completely different Prince. DNF.

Dragon Age 2 ruined Dragon Age for me.

Mass Effect 3's ending soured me to anything EA until Titanfall 2 was less than $20.

I'm sure I'm forgetting a few more ones but those two stand out the most.

Not necessarily beloved, but I hated the tone and genre shift between Jak and Daxter and Jak 2. I hated the driving sections so much, that that's where I put the game down. Looking back, I guess they wanted to make a different game, but had to make a sequel?

Oblivion.

Daggerfall was awesome and Morrowind blew me away. Going into Oblivion I had the highest hopes. Bought the Collectors Edition, took the day off....and biggest disappointment from a game ever. Granted I like Skyrim. Not as much as Daggerfall or Morrowind, but far more than Oblivion. So I guess it didn't kill the franchise for me.

Bonus popular game that actually killed the franchise for me: GTA4. I loved the Trilogy, but I could not stand IV. All the main characters annoyed the piss out of me, the driving and gun play weren't nearly as fun...I tried to play it but got burned out around 1/3rd of the way in. Tried to play GTA5 a few years ago and I felt burned out after 40 minutes.

I don't think it would be possible for a bad sequel to ruin a game I liked.

Metroid Other M has not ruined previous Metroids for me (its terrible Adam Malkovich depiction doesn't even register when I'm playing Fusion, since the character has barely any continuity between the two).

Okamiden did not ruin Okami, it just sucked on its own and what little story it tried to change I disregard. I'd replay Okami today in a heartbeat.

Xenoblade Chronicles 2 took a direction I hated, both in style and gameplay, and it made me want to replay XC1. I did. It's still awesome, though XC3 became my favourite.

And complete opposite of the topic : Baten Kaitos was not bad, but kind of a silly popcorn game to me. Baten Kaitos Origins did not ruin this game : it was so great and flipped the interpretation of the first game so well it made BK better.

Sacred 3. It was a soulless cash grab that had nothing to do with the previous game, which is one of my absolute favourite ARPG's.

I see op choose the circle jerk today. Excellent choice, Excellent pallet 🤣.

The Legend of Heroes: Trails from Zero.

In a lot of respects it’s a good game, its fans even love it as a part of this big ongoing series. But it repeated a few tropes and trends that really started to get to me; wherein so many villains are introduced in a Dragonball style of escalating power rather than character definition.

The first two games introduced one supremely powerful hero, but invented mature and elaborate reasons as to why he couldn’t save the world alone - why evil or influential forces need cooperation of everyone to defeat, not a single showy swordsman. Then, later games try to impress you by showing villains that could easily beat this hero; without character definition to make such claims worth it.

They also really sold into the anime gender tropes - where every woman makes shy/teasing comments about the male lead, most girls are lesbian only for the sake of sexual harassment rather than true connection, etc.

This is going to show my age but Master of Orion 3.

Renegade III: The Final Chapter.

Renegade on the ZX Spectrum was good, the sequel Target: Renegade was one of my favourite games for years, but the third game was a cynical cash grab, badly executed, barely playable.

Hal0 4 and Below Zero come to mind. Facebook buying beatsaber and ruining it with their filthy little hands, too. It took a huge nosedive in quality.

Beloved is a REALLY strong word.

But, Mortal Kombat 11. I had always enjoyed the MK games (it helped that my sister owned the N64 so I only played maybe a grand total of two hours of the wannabe Tekken ones...). And the timeloop reboot had reinvigorated the series and I was a much more accomplished fighting game player and actually understood how to push through projectile spam.

Then they randomly recast Sonya Blade with (sandy hook truther and terf) rhonda rousey and it was just... ugh. Even ignoring she is a hateful and evil shitbag... she is just a REALLY bad actress. Could never bring myself to grab 11 and by the time "1" came out I had also realized that I actively disliked the x-ray attacks and finishers since they were just boringly gorey time sinks.

And honorable mention to Splinter Cell Double Agent. But apparently the OG xbox/wii u (?) version of that was actually good and it was just 360/PC that was a steaming pile of shit. And Conviction was a very different game but also I still think about the aftermath of the EMP every so often.

Metro Exodus. Opening up the map was a mistake. The linear levels were fine, that gives you tight pacing and you always know what's next. The confined underground spaces were part of the soul of that series. I only played maybe 8 hours of Exodus and can't be bothered to play more.