FFI: Elfland, one giant fetch quest/chain of deals with no plot significance and it all happens when the game decides to crank up the difficulty, introduce poison status, and jack up all prices. Not a fan.

FFII: Hunting down the masks to get into Ultima Tower. Boring quest, with awful dungeons and it's ultimately just padding for the game.

FFIII: Honestly? The last stretch of the game with the triple threat dungeon (four dungeons if you do Eureka as well) and death is painful with the games limited save options.

FFIV: Tower of Babil and the Sylph cave.

FFV: Probably the Pyramid and some of the early sections of the last world. It was kind of easy to see the team was running out of ideas around then.

FFVI: Mt. Kolts and chasing down the Espers in Thamasa.

FFVII: Cosmo Canyon and pretty much everything after Disc 1.

FFVIII: Esthar and pretty much the rest of the game.

FFIX: The entire quest to find entry into Terra.

FFX: Everything between leaving Luca until you reach Zanarkand. If I had to pick one specific point, Mihen Highroad, and Operation Mi'hen

FFXI: The long hours of reading the Wiki to actually figure out how to do anything.

FFXII: The Great Crystal or the Yensa Sandsea.

FFXIII: The whole damn game.

FFXIV: Listening to my friends rave about it and how I should check it out despite my many admissions of not being big on MMO games.

FFXV: Everything before Titan, the early chapters are seriously light on plot.

FFTactics: Chapter 4, when the Lucavi plotline overtakes the actual good part of the story.

Tactics Advance: The early game when very little happens.

TA2: The Story missions in general.