Hated then Loved:
Monster hunter. My very first was Monster Hunter Freedom 2 on PSP. Played a bit of it and ended up getting horribly frustrated with the combat. I was struggling with killing just a Giadrome. I ended up shelving the game, ruling it as "not for me". Maybe a year or so later I found Freedom Unite on the shelf in a store, and for SOME reason I picked it up despite knowing that I disliked 2. That started the spiral. Something eventually clicked and I played through all of it. I went back and played through the First game on PS2 and kept playing more and more of the series. I loved the series since.
Sekiro : Man getting used to this game was a huge chore. I almost refunded the game on steam due to it. The combat while very similar in feel and control to Soul's games, is nothing like them. I couldn't adapt. I watched one video of someone (I forget who it was), showing me exactly what I'm doing wrong, and that's all I needed to figure out the game. Eventually I tried again with a fresh mind and it clicked. Now its become one of my favorite games in From Software's library.
Loved then hated:
Hardest question as I've enjoyed most everything Ive played. And everything I'm about to list I still enjoy to some extent. But If I had to go back and say which games I enjoyed less the longer I played them. Then I have a few in mind.
Breath of the Wild : I enjoyed what I played however much of the game falls apart for me when the gameplay loop defaults me into finding Shrines and exploring a very empty world. Too much open space with not a lot in that open space. The core dungeons from the Divine beasts had very interesting concepts, but you spend 5 minutes in each of them, with a "blobby" monster at the end that looks identical to the other 3. Combine that with the weapon degredation, and many many other factors. The longer I played the game, the less I enjoyed. I haven't played the game again, and I have 0 interest in returning to it.
Dark Souls 2, 3 and Elden Ring : Blastphemous to say I know. Much of what I enjoyed with the souls games, exist in Demon's Souls and Dark Souls 1. Primarily Demon's. Bosses were far more interesting in design and gameplay. They weren't all health sponges, or bosses where the cycle was "go in roll and parry" to win. Demon's had variety of environmental tricks with many of their bosses that would give you an advantage. It was far more interesting and engaging when I have a boss that's blind, and I learn how to take avantage over him and his environment.
For my overall opinion, just look at
Mathewmatosis' video on this subject. It basically mirrors how I feel about this series. He can explain it 100x better than I ever can.
Elden ring falls under this as well, but even more egregious.
Again, none of these are bad games, and I've enjoyed them too. 70+ hours in breath of the wild, and well over 100 hours in each of the souls games/elden ring. They just all apart the longer I played them. And honestly, I dont think I'll return to em like I have with other games.