Here is the full list of all 8 Lumber King achievements.
The first time you hit a tree.
For you failed to kill that tree.
You unlocked "Angel Lee".
Said the Iron Folk Tony.
You got the skill "Psychic Of Lumber King".
You did a million damage with one shot.
You cleared 20-5 and now it's all sands.
You fed the developer with all DLCs in your storage. Now all your damage will be doubled.