This Seeking Tech guide will show you how to easily unlock the On Your Marc-o trophy and achievement in Metal Slug XX.
To unlock this, you need to “defeat 30 enemies with Marco’s Punching Glove Special Action.”
Use the following video as a reference:
To start off, head over to the beginning of Stage 2.
When heading down the elevator, jump to the right and then ignore the enemies. You would need to destroy the right-most crate without hurting the nearby enemy.
Another crate should then drop on the left side of the screen, next to the soldier with the siren. Break that crate to trigger a fight with the 100 Morden Soldiers.
You can then use the Punching Glove Special Action until this trophy is unlocked.