* King Boo broke out of his painting ON HIS OWN. Yeah, he's definitely far more competent than Bowser.
** Also the fact he didn't resort to anything other than his own power to fight you.
* Poor Luigi always shivers at the mere thought of a ghost, yet keeps pushing forward anyway, even long before [[spoiler:he found out his brother was kidnapped.]] That's how badly he wanted to be a hero and he pulled it off magnificently.
** It's subtly implied that E. Gadd went to Mario before requesting Luigi's help, [[spoiler: which would explain his being captured.]] Looks like E. Gadd was right about stepping out of his brother's shadow.
* Holy crap, does King Boo pull out all the stops to get ol' Weege this time around. [[spoiler: When you abduct someone mid-teleport even at the risk of losing the MacGuffin that could thwart ''all your plans'', you're gonna be out for blood, and King Boo's restrained snarkiness showed little different.]] Alone, trapped in complete darkness, stranded in a pocket dimension of which the very fabric is controlled by a being who you know absolutely ''despises'' you. What does Luigi do? He mans up, swallows his fear and takes the fight to King Boo on a turf where he has absolutely no advantage to speak of. Nobody can question if this CowardlyLion has some serious brass ones.
** Also, King Boo even manages to fool and catch '''[[TheFourthWallWillNotProtectYou the player]]''' off guard, by doing things like [[spoiler: making it look like E-4 was an end-boss stage where you fight King Boo]]. It's not as much Luigi, but still.
* The fifth boss is one for Next Level Games. [[spoiler: It's basically Boolossus done right. Then, for the Three Star rank, it becomes just as hard as Boolossus was.]]
* Defeating a Boo... in a room that's extremely narrow.
* The third boss, ThatOneBoss-worthy as he is, nonetheless gets points for some pretty clever CombatPragmatism: [[spoiler:Instead of just possessing something specific like his brethren do, he actually possesses the whole arena -- the Belfry Clock -- itself.]]
* The penultimate boss deserves mention, too. The possessor for this fight pulls off a trick none of the others had yet managed; ''splitting itself'' to form a WolfPackBoss with a few suits of armor. After going a few rounds that way and being put on the ropes, it then proceeds to one-up itself by flying out of the mansion... and possessing a [[AttackOfTheFiftyFootWhatever gigantic suit of armor]] to try to squash Luigi.