YMMV / Mario & Luigi: Kola Kingdom Quest

• Breather Level: It's not easy, but the second secret level in Metal Kingdom is a cakewalk compared to pretty much everything else in that world (see That One Level below). World 5 is at least a downplayed version; aside from Roy's castle and any time Hammer Bros get involved, it tends to be rather simple to get through (especially if you consider World 6 a Difficulty Spike).
• Checkpoint Starvation: Not a problem for most of the game, but the final castle stands out, with three sections of decent length, the second of which is easy but time-consuming and the third of which is an Auto-Scrolling Level with tricky platforming, and a two-stage boss battle. The only checkpoint is at the end of the first section. The level can easily overstay its welcome as a result.
• That One Level:
  • 3-3 and its puzzle-ish nature can catch one off guard the first time, especially during the final area. It's also noticeably more time-consuming than most of the levels around it.
  • Thunder Lakitu's fortress is surprisingly difficult for World 4, especially when it starts auto-scrolling, and the boss is one of the few that actually puts up a fight.
  • 6-1, surprisingly, for being an introduction to the world concept that doesn't pull any punches right from the start.
  • Ice Birdo's Fortress. Slippy Slidey moving platforms!
  • 8-3 and the World 8 fortress (hmm, a lot of the fortress levels seem to fall into this) have a lot of tricky platforming and some very nasty combinations of enemies and obstacles, which is compounded by the excess of conveyor belts making it hard to position yourself and avoid getting dragged right into a Bottomless Pit, spikes, or crushers.