Guacamelee! 2

First, to unlock the Cascorrona skin, you have to get a gold medal on the Face Invaders challenge. Then teleport to Templo de la Serpiente and go up the shaft and take the 2nd right hallway. There are A TON of enemies in this room so you should be able to get the achievement in no time.



EDIT: If you're going to down vote, tell me why so I can try to make the solution better. Help me understand why you would down vote this solution when it includes everything you need to get the achievement.