These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: New Super Mario Bros. 2
Breather Boss: Morton Koopa Jr. You don't even need to move to win this battle.
Hilarious in Hindsight: in an odd, not to mention interesting, shorter-than-usual-time-gap instance of this trope, there's the official announcement - the game's "ultimate (albeit optional) goal" is getting one million golden coins.
Which is odd because the Mega Mushroom returns in this game, but has been nerfed. It only appears in a few levels, you cannot rack up lives via property damage, and you can't take it to any other level. The Gold Flower however? Spend five Star Coins on that shit, waltz yourself to whatever stage you want, and blast everything in your path while racking up some cash. Even Bowser goes down in one shot.
It's Easy, so It Sucks: One of the most heavily criticized aspects of this game was the lack of challenge. Getting to Bowser is pretty much a cakewalk; the game doesn't get noticeably difficult until you get to the bonus worlds, and even those are not as brutal as we've come to expect from this series.
Nightmare Fuel: There is nothing okay about the giant Boo (Boohemoth) that follows you through most of the Ghost House in World 2. It's huge, it has a terrifying face, it doesn't follow typical Boo rules (it will inch forward even if you look directly at it), and if you touch it? Instant death.
That One Level: A few of the warp cannon levels can be nightmares, especially World Flower-Cannon.