I spent a good chunk of early 2019 grinding the Kingdom hearts platinum in anticipation for KH3 and it severely tried my patience.
Birth By Sleep's list in particular does everything in its power to waste your time, by 100%ing the game with 3 characters in 3 separate playthroughs, on top of having one of the most bullshit, poorly designed optional bosses in existence.
Crash N Sane trilogy was also quite time consuming in grinding those time trials.
My latest effort was platting Judgement and that game basically want 100% completion involving some major grinds, revolving around things like drone racing and the king's ransom needed to buy all mods, and our good friend mahjong. I thankfully paced to plat through my first playthrough so I wasn't overwhelmed post game
Some are more out of time consumption, but Tales of Vesperia was rough. You need to get every title in the game, which is tied to doing essentially everything, like a title for having all the equipment in the game. Turns out a ton of this is tied to very easily missed side quests that are time limited and require backtracking at odd moments, certain towns that sell a special sword only once and then it's never found again. It also had an achievement for speedrunning the game (you can't skip text...), and another for beating the first third of the game at a very low level, so the game took like 4 playthroughs and it's a long RPG. Why did I do any of this.
I did this as well, and it is a serious investment on top of basically 100%ing the game which is no mean feat. The Colisseum grinding alone took ages.
Mini game master in Yakuza 3. Basically do every single mini game to completion. Takes an extreme amount of time invested. And some of them are very difficult and annoying. Had to put a piece of tape on my screen to help me do the batting I remember.
I've been playing all the Yakuza games on PS4 and did this some months ago. The gambling grind is annoying enough, but few if any of Yakuza 3s minigames still hold up well.
Yakuza 4 basically expected the same minigame completion grind to get the golden gun, but since that actually didn't have a trophy attached, I was like NOPE!
Assassin's Creed Odyssey was a really long plat, but it helps that I did most of the trophies naturally just enjoying the game and only had a little to clean up.
With DLC included, this just took ages for me. I actually quit for 3 months just because I burnt out. Origins I got 100% in a fraction of the time including all DLC.