OMORI

When you meet Space Boyfriend for the first time, and have to find his mix tape, a door to the left of his bed will appear. This leads to his backyard. Upon entering the door you'll be on a bridge, with planets floating around. Go right, and eventually you'll see the earth. Interact with it, and choose to disturb it. Defeat it to get the achievement, took about 30 seconds after the battle was over for mine to pop. Be wary of Earths Ultimate Attack, it hit me with it right when I was about to defeat it, doing roughly 30 damage to everyone. So keep your health up and you won't have any problem. I don't know if this achievement is missable or not.