New Super Mario Bros. 2/World 6-Castle

Boss: Bowser
As soon as you reach the hall, Bowser will breathe fireballs at you until you reach the end of the hall. After you reach him, the battle begins. First, Bowser will move toward you, then he'll do an attack against you (or do nothing). After that, he'll move backwards, then do another attack. He'll then repeat the same cycle over again. The attacks Bowser has are: Breathing a fireball at you, breathing multiple fireballs at you, doing a small leap and breathing a fireball at you, throwing hammers at you, and doing a giant leap in the air.

To defeat him, either wait for him to do a giant leap and then run past him or shoot fireballs at him until he gets fried (requires a fire flower to do this). Then, hit the "!" switch on the other side. Unfortunately, your victory is short-lived as those nasty Koopalings will use their magic wands to make Bowser giant. Now, the true battle begins!

This time, you must jump on floating platforms to avoid getting burned by the rising lava. To make things extra spicy, Bowser will attempt to claw you by slashing his claws on the row of platforms you're on. As soon as Bowser raises his claws, he'll lock on the platform you're currently on. Immediately jump onto a different column of platforms. While Bowsers claws don't hurt you, they destroy the platforms, potentially making you fall to your death (the lava). Keep doing this until the screen stops scrolling and you jump to the very top of the screen. You are now on a safe platform, safe from the lava for a little bit. Afterwards, Bowser will attempt to breath flames on the floor from left to right. Go near the right wall, and with a running start, jump over the flames. After that, the lava rises again and the floating platforms appear again. Do the same thing, except this time, there will be Bowser statues breathing fireballs at you. Watch your step! Also, on the second safe platform with no lava, Bowser will breath flames on the floor twice before the lava rises again (first, from left to right, then right to left). Again, do the same thing that you do did on the first no lava platform, except when Bowser breathes flames the second time, start near the left wall before jumping (remember to have a running start before jumping). Repeat until you reach the giant "!" switch. Hit the switch! Bowser will then start sinking and will eventually collapse to his death. Congratulations! You rescue Princess Peach and rid of Bowser entirely (for now, at least)! You win and now you can Save instead of Quick Saving!