Regardless on your stance on Kojima himself and his involvement, Metal Gear Solid V certainly caused a massive ruckus to Konami's reputation.

Bioware DAI and MEA
Guerilla Games Horizon
Santa Monica GOW4
Capcom MVCI and SF5
Gearbox Borderlands 2 and Duke Nukem Forever (i like it but barely anyone does)

Grabbed by the Ghoulies really stained Rare's reputation. The games that followed didn't do much to restore it. Donkey Kong Country was, of course, the game that built that reputation to begin with.

Final Fantasy VII really supercharged Square's reputation in the Western world. They were little more than a cult developer among Americans prior to that.

Prince of Persia for Ubisoft, at least outside of France.

Turok on N64 gave Acclaim a few years of respectability without Midway arcade ports. BMX XXX was the nail in the coffin for them.

SimCity started Maxis's rise to fame, SimCity 5 killed it.

Persona 4 helped get Atlus into the mainstream, though they were respected among their fanbase. P5 was a bona fide hit.

Oh, and Donkey Kong for Nintendo.

Wasn't being bought by EA that killed Maxi's?

Sonic Team is one that sticks out to me the most; they've flip-flopped like twice and they had a ton to prove after leaving such a bad taste in peoples' mouths due to Sonic 06.

Unleashed was definitely not perfect for obvious reasons, as well as unrefined with strange game design decisions like mapping the homing attack button separately from the jump button and Sonic being tricky to control even during the day time stages. But, the game was so ambitious in story and aesthetic; it's still probably the most ambitious Sonic game to this day, as deeply flawed as it is.

Colours took what was great about Unleashed and expanded it somewhat and became a very well received Sonic game; a good one for a long time at the time. Generations did more of the same, but even better. At that point, Sonic Team had mostly won back peoples' trust in them after how good those games turned out; a lot of people thought they knew what's working out and what's good and expected them to expand on what they've established and they picked themselves back up after the disastrous Sonic 06.

But no, they choose to throw out everything they built up and try out ANOTHER different gameplay style for Lost World because they felt the need to be innovative for the sake of it. The parkour system obviously didn't work out well; controls was confusing and wonky with level design that didn't mesh well with the gameplay style and is probably some of the worst level design in a Sonic game at the time. Parkour was mostly redundant and was only required for collectibles cos there was invisible springs in areas where you could parkour your way up if you only wanted to complete the level; it gives off the air that the devs had no faith in their parkour system to begin with. Lost World also did more nostalgia rehashing, soon after the anniversary game Generations, with uninspiring levels and enemies.

Sega touted Sonic Forces as "From the team that brought you Sonic Colours and Sonic Generations" which gave us hope. Which was false cos it turned out almost no one who worked on those games returned to work on Forces; it only had three level designers, two new and one from Lost World. The game wasn't terrible, but it was incredibly uninspiring, insultingly easy, bland and boring; that's worse than a bad game like Sonic 06. At least Sonic 06 is amusing in what ways you can screw and glitch the game up, for how poorly put together it was.

The big offender though is that Sonic Team can do so much better than what they did with Forces, and should have learned from their mistakes and lessons by now after past successes and failures, regardless of whether the same or different people worked on those games.

A lot of people started trashing GG with Killzone Shadowfall.

Now with Horizon they are all of a sudden seen as one of the best devs in Sony's corner (not that I ever had my doubts, they just needed to expand beyond FPS).

Not at the time. Keep in mind they got bought up in the mid 90's, when EA was still one of the best publishers. Under EA leadership Maxis first brought out Sim City 3000, then the first Sims, both very acclaimed titles. It's only with The Sims 3 that it began to tarnish

I'd like to pinpoint the rise and decline of Rareware, I think it can be argued that DKC really put them on the map, they had a long period of decent success mixed with failures even before they were called Rareware, but I don't think any of that compared to how their status changed after DKC.

I can't narrow their downfall to a single game, maybe Grabbed by the Ghoulies or perhaps Starfox Adventures, it could be Banjo Kazooie Nuts and Bolts that finally made fans give up but it seemed like a long period of continual disappointment.

I didn't know it was so long ago,