Ultimate Collector Achievement
Unlock all the collectible pieces
Collectible pieces are unlocked by completing various objectives in the game. If you play through the game and get the rest of the achievements then you will be doing a lot of the actions that result in collecting pieces. The one that people often miss is for kicking 300 keflings. To get this last quest, simply kick 300 keflings in the forest world and then a quest should appear, that upon redeeming, should give you an emote and heart.