- Wario Land: Super Mario Land 3
- The very first boss is one of these, being a fairly difficult boss for so early in the game. One hit makes attacking him nearly impossible, he's pretty quick in attacking and attacks from land, the ceiling and underground in various phases. Also a rather harsh Wake-Up Call Boss.
- Devil's Head can, fittingly enough, go right to hell. He has two attacks, spitting a rock which you need to throw at him to attack him and tonguing the ground to destroy platforms. What makes him so difficult is he's strictly a Luck-Based Mission: he picks his attacks at random and there's no way to provoke specific ones, so if he just happens to destroy too many platforms he'll Unwinnable by Design. Since his projectiles need to bounce once to be picked up, it's very easy for him to just keep spitting them into the lava below if he even destroys only a few platforms in the middle.
- Later on you face Bobo, the giant bird of the S.S. Teacup stage. Your only means of attacking him is stunning the smaller birds he throws at you and throwing them back, it's incredibly easy to get hit doing this and you only get two hits, and Bobo quickly blows them away if you don't grab them in time. You'll have a bit easier of a time if you figure out how to stun the smaller birds from belownote but you can still expect to die at least a few times before you pull it off.
- Captain Syrup's fireball-throwing mech in Wario Land 2 takes multiple hits, and has a very tight time limit to avoid the flames shooting down and bursting up from the floor to launch you into preceding rooms. Getting hit once restarts the whole fight.
- The sorcerer fox, Wolfenboss, in Wario Land 3, mostly because hitting him involves bouncing an enemy off the walls, and because his projectiles are extremely difficult to avoid on the last hit, but you can still expect to lose at least a few times before you manage to pull it off.
- Also, though not as hard as Wolfenboss, since it is very easy to avoid losing, Shoot the Soccer Bunny is a slog to beat. The turtle guard is, ironically, quick to leave his stunned state, so that you hardly have enough time to stun Shoot into ball form and punt him into the goal before the turtle pops back up. This is not helped by the physics being a little wonky, making it easy to accidentally keep bumping back Shoot when trying to jump over him, wasting even more time. Though you can punt Shoot into the net even if the turtle guard is not stunned, the timing is very tight.
- From Wario Land 4, you have Aerodent, a giant teddy bear balloon being piloted by a rat...thing. Aerodent floats overhead, throwing down Spikebutts, which you have to flip over and throw into a patch (with wonky collision detection) to deflate Aerodent. Then, when it drifts downward a bit, you hit the feet with Wario's barge attack to flip it over, then FINALLY you can hit the rat a couple times before it reinflates the bear and floats back up. And as you repeat this process, it throws down fireballs, which turn you into Fire Wario, which just wastes time. The only way to get a perfect score for this boss is to grind medals and get the Large Lips to take its health down to two hearts, and it's still a difficult fight.
- There's also Bloomsday/Scumflower in Wario Land: Shake It!, who is probably the one boss in the game who takes the longest to defeat (three different attack patterns), can cause earthquakes and hurricanes to mess you up, and has to be very slowly knocked backwards off the edge by throwing enemies and then quickly attacking him a few times.
That One Boss / Wario Land