Mario went off to pursue Bowser at the Super Mario Maker stage. When he got there, Bowser was already there waiting for him.
Bowser: So you finally decided to show, did you?
Mario: What are your intentions, Bowser? Why are working with Master Hand again?
Bowser: It's not my job to tell you. Me and the other villains have own purposes with him.
Mario: I won't let you achieve your goal.
Bowser: Of course, Mario. You always contradict me and my ambitions. Which is why we are going to settle it in smash.
Mario: You are going to get defeated.
Bowser: Personally, I think you're the one who's going to taste defeat. If you haven't noticed, I've been lifting 350-pound weights for 2 hours straight each day.
Mario attempted to throw a fireball, but Bowser fiercely and confidently punched it away.
Bowser: Bwah, ha, ha, ha, ha!
Bowser came running towards him and knocked Mario offstage with a Dash Attack. Mario was able come back onstage.
Mario: I won't stay down that easy.
Bowser used Bowser Bomb, but Mario rolled away and executed a Side Smash. Bowser was able to keep his ground and was charging his Side Smash, but Mario caped him and did a Down Smash, making him fall in a pool of lava.
Bowser: Rrrrrraaaah!
Mario side taunt.
When Mario was about to leave, he heard a loud rumble and when he turned around he saw Bowser in his monstrous form, Giga Bowser.
Bowser: You should just turn back, or be a man and take me on!
Mario: You're on!
Mario was running towards him in ambition, while Bowser was just standing there waiting for him to strike.
Bowser: Not even a challenge...
Mario then got the idea to get ahold of Bowser's tail but was soon smacked into a wall by the tail.
Bowser: Foolish Mario, what do you think this is? Super Mario 64? This is Smash Bros! Get up and fight me!
(Yes, I don't care if I'm breaking the fourth wall)
Bowser launched Mario across the stage and was going to land in lava until the Mario Maker created a platform for Mario to land on.
Bowser: What was that? A giant random hand appearing out of nowhere! Forget it. Mario, you're going to be so sorry you've interrupted with my plans!
Bowser came running towards him coming in with a dash attack. Mario rolled to the other side. The Mario Maker came and dropped in a Smash Ball. Mario got it, and Bowser didn't like that.
Bowser: Koopas, Goombas, Shy Guys, help me! Protect me from Mario!
Bowser's minions try to ambush him, but those enemies were just way too easy.
Bowser: Dang it!
Unexpectedly, Bowser's Giga Bowser form wear off.
Bowser: Noooooo! I'm not finished yet!
Bowser launched 1,000 fast bullet bills towards Mario, but Mario had a proud and confident smirk.
Mario: Oh yeah! Hiyyahhh!
He unleashed his Final Smash, Mario Finale.
Bowser was defeated and was trophylized. A Warp Pipe appeared and Mario went through it going back to Final Destination. Soon after he left, Bowser's trophy disappeared.
Mario, Donkey Kong, Link, Samus, Yoshi, Kirby, Fox, Pikachu, Luigi, Captain Falcon, Ness, Jigglypuff, Peach, Zelda, Sheik, Marth, Mr. Game & Watch, Dr. Mario, Falco, Roy, Meta Knight, Pit, Zero Suit Samus, Ike, Charizard, Diddy Kong, Lucas, King Dedede, Olimar, Lucario, R.O.B., Toon Link, Villager, Wii Fit Trainer, Rosalina & Luma, Little Mac, Greninja, Palutena, Robin, Lucina, Shulk, Duck Hunt, Sonic, Mega Man, Pac-Man, Ryu joined your team.