A few old time recommendations
Yes Minister/Yes Prime Minister (clever political satire)
Sherlock Holmes (specifically the 1980s show with Jeremy Brett as Holmes - easily my favourite SH actor)
Inspector Morse (I like old school detective shows)
Coupling (my favourite classic sitcom)
I have two (and I apologize for the pain I cause, if anyone decides to watch them after my recommendation)
Grave of the Fireflies
Come and See
I'm honestly still not sure which one is the the most difficult to watch, but they WILL make you feel something.
I often like them - in theory. When it comes to playing it, they often get extremely repetitive, and sometimes with no clear indication of what's required to progress in the story.
I almost exclusively play Ren'Py. It takes something out of the ordinary for me to even consider trying a different engine, and even then I'm often too annoyed with how the game works, so I usually end up giving up on the game pretty fast.
I'm not sure I found it, but the first I played was Daughter for Dessert, which was kind of annoying but I still knew I had to find more of this stuff. Soon after, it was Milfy City that really got me hooked.
If you mean a long and annoying grind few people enjoy, but everyone keeps going for the greater good, I'm reminded of World of Warcraft, when whole servers had to cooperate to open the gates of Ahn'Qiraj. What a long slog that was