Beat the Minions!
From the Super Mario Wiki
Beat the Minions! is the final post-game level of the Bowser Jr.'s Journey mode of Mario & Luigi: Bowser's Inside Story + Bowser Jr.'s Journey, and by extension, the final level of the entire game.
Each round has a dark, Malatone Formula:X-infected Koopaling as the enemy captain, with all rounds but the first having a second dark Koopaling as first officer; they all use the same Captain Commands as their normal versions (apart from Ludwig's Negotiate). The last round of the mission has all of the Koopalings as troops, with a dark and infected Bowser as the captain; he acts as a Melee-type unit. Almost every other enemy in this level is affected with Malatone Formula:X as well, apart from the three enemies at the back in rounds 1-4.
After completing the level, Bowser Jr. and his troops will briefly celebrate while the game congratulates the player for completing the entire quest.