My friends and I are all GMs and all run various campaigns for each other, primarily Pathfinder and D&D 5e, but we are still constantly looking to improve our skills and techniques as gamemasters. I threw around the idea of creating a sort of milestone list of what could be considered major accomplishments in the life of a GM, which they really liked the idea of. Things like: bringing a player to tears (whilst remaining in character, not from doing something mean/dickish at the table), running a full campaign to completion, your first permanent character death, a TPK that is entirely the party's fault, etc.

What all do you consider to be the major, outstanding, or just emotional milestones/accomplishments that one will go through in the life of a GM?