It's almost 2028. Jim Davis realises he's not going to last much longer. He decides to end the Garfield comic, as he doesn't want his creation to be left without him and possibly lose the charm it had.
For the entire year of 2028, Jon and Liz are increasingly getting worse in their relationship. At first, it's simply Liz getting annoyed at times, and it eventually escalates to any strips with them together having a very negative vibe, with Jon trying to salvage any happiness while Liz simply wishes she wasn't there. She's even meaner than the original Liz was to Jon.
The previous 10 strips before that one strip revolve around Liz breaking up with Jon, and him not knowing what to do with himself. Garfield doesn't take anything seriously, only thinking about the fact that Jon is too depressed to feed him. Odie doesn't notice anything.
One such strip is published on June 19th, 2028. News articles pop up everywhere. Wyatt Duncan, the creator of the @GarfieldFanArt Twitter, tweets out nothing that day except for "Alrighty then". Garfield is the top trending topic on Twitter. Wikipedia staff locks all Garfield related pages due to massive edit waves. Garfield.com has a 1-day-long outage due to server overload.
The next 5 strips, all in black and white, revolve around Garfield and Odie trying to figure out what to do with themselves. Liz comes back on the 22nd. The first panel has no dialogue, and is simply Garf and Odie staring at the floor. The second panel, Liz comes into the house out of view (still having a key) saying "Jon, are you here? Can we talk?" in the first panel, as Garf and Odie's eyes widen. They look at each other still wide eyed in the third panel, and Liz says "...Jon?"
The very last comic was on June 25th. The banner art usually seen in Sunday comics at the top is a series of images of Garfield walking with a gloomy expression, with each image becoming more and more transparent from left to right, and the usual Garfield text does not appear. Garfield and Odie accept that they can't survive in the house any longer, being completely abandoned by Liz and anyone else who came into the house. They both agree that their best option is to go become strays. They look around a bit, pack up some things, walk out of the house, and down the road. The first hint of color since the reveal of Jon's death is seen, with the sky above them in the very last panel being slightly tinted blue. This is believed to be hinting that Jon brought color to Garfield's life, and now his color is in a place beyond.
This ending was extremely controversial. Some said that Jim touched a much too serious topic for a family-friendly strip, while others praised him for giving the strip a very emotional ending which people would never forget. Many people in defence of the ending cited the series of comics from 1989-10-23 to 1989-10-28, which were much more serious than every other Garfield comic. Some theorised that this ending was planned from the very beginning, and that series of comics is actually taking place many years after the ending as Garfield comes back to the house and loses his mind.
Jim Davis lives the rest of his life happily, spending time with his family, and occasionally still writing personal comic strips that aren't Garfield. He dies naturally at the age of 95, leaving a note by his bed thanking his family, friends, and fans for giving him a life he could've never imagined would've happened when he was young. His grave has a specially-made Garfield sculpture that resembles the original 1978 Garfield. All Garfield media production has ceased as of Jim's wishes, including any sort of brand deals, movies, or apps. Garfield.com is left running as a archive of Jim's legacy, including all strips he's ever published (including Gnorm Gnat), and listings of all Garfield games, movies, TV shows, etc. Eventually, Paws Inc is shut down due to a lack of money, Garfield.com officially shuts down, and Garfield enters the public domain a few years later.