Loot Hero DX

This Achievement unlocks for buying one upgrade for each skill, Attack, Critical, Defense & Speed.

You can grind any level by killing enemies to get coins by going to the right side of the level and then back to the left side and the enemies will keep respawning just make sure that you don't kill the boss or else the level will end.

I show a coin grinding method in my Achievement Walkthrough starting at 2:01 minutes into the video.

Just buy one each of the upgrades (Attack, Critical, Defence & Speed) at one of the many Houses as you progress through the game