In order to unlock this cheevo you have to defeat one of the first mini boss.
As soon as you unlocked the frog splash you will encounter the skeleton luchador :
It's not so difficult , but i can suggest you to reach the upper platforms and start to smashing him with the freshly new unlocked skill ( jump with
and then press together
+
) . Watch out when his fists start to brights because he will going to attack you ! Pics related