Final Boss, 2 Turns - Mario + Rabbids

The final boss of Mario + Rabbids done in 2 turns.

Characters:

Mario
Rabbid Mario - His Boom Dashes combined with the high damage Boomshot allow the team to defeat phase 1 using only two attacks. Magnet Dance also lures in Bucklers to shoot Bowser.
Luigi - His team jumps are needed to get to a high ground spot on turn 1. Steely Stare is also needed to deal a lot of damage to Bowser as he shifts to phase 3.

Notes:

-During phase 2 and as Bowser flies to the center of the map for phase 3, characters can get a high ground damage bonus on Bowser if they stand on certain spots on the map. Since this was a recently discovered glitch, I'm not sure what spots give a high ground damage bonus. All I know is Luigi's turn 1 ending spot and and tile to the left that can give high ground versus Bowser if he is in that northern area. There's also a high ground damage bonus on Luigi's second and third Steely Stare shots as Bowser flies to the center from the right side for phase 3.

-This is not the only way to beat this level in 2 turns. The level was first beaten in 2 turns about two years ago. It does not use any glitches, but it takes a lot more regular RNG and has to use Fire RNG since Yoshi needed to be used.

-Extra Health mode is not required, but it may mess with your ability to beat the level with all heroes alive.

-Mario uses the Bounce on his Melee weapon to knock Rabbid Mario close to where he wants to move on turn 2. He also avoids the Pyroclasts this way.

-The Valkyries' Burn Super Effect may displace your characters. It usually isn't a problem in my experience.

-In some scenarios, a Valkyries might move close to Bowser. Rabbid Mario can attack both of them at the same time with the Boomshot. Doing this will deal extra damage to Bowser since he used Protection on the Valkyries. This can be helpful for reducing the RNG.

If you don't get enough critical hits to defeat Bowser before he flies to the center for phase 3, the Bucklers may be able to finish him off for you. There are two Bucklers that will hit Bowser with the Boomshot, and one will damage Bowser through a Boom Dash. This will do about 200 damage. Rabbid Mario lures in these Bucklers with Magnet Dance for them to target the team.