Ori and the Blind Forest

Ori has three different skill trees that you can upgrade using ability points earned from ability orbs. Everything you kill increases your ability orbs and once the yellow circular bar in the bottom center of the screen (Between Energy and Life) fills up you gain a point that can be spent on a skill. The Combat Tree is the Lower/Left most of the three upgrade trees, all the early skills cost only one point while a few of the later ones require 2 and the final 2 skills take 3 points each to purchase. Once you buy the final skill which gives you a Spirit Flame Target upgrade this achievement unlocks.