I beat The Black Heart, Atheon, Crota, Oryx, Siva, Xol, Ghaul, Calus, Riven, Nezerac, Savathun, and The Witness, plus AlakHul, Atraks, Sepiks, Taniks, the Forsaken Baron, a bunch of Vex Gatelords and Overminds... I rediscovered 3 Dark Subclasses plus a fourth Light one and then merged them, I became an Iron Lord, a Dregden and went to Osiris' Lighthouse in D1 and D2, healed the Traveller (twice), I witnessed my own funeral in the Corridors of Time, bringing back Saint 14, I saved and killed Rasputin and Prince/Crow, became Taken and beat Sword Logic, Vex Simulations, and Nightmares themselves: including the real world that's four entire realities I conquered and I communed with The Long Boi In The Soup. I saw the whole story through. Anything that happens now is of lesser concern, so I can leave.

For me the big mistake started with the Dreaming City: when the world first raid changed the game for other players- I wasn't the main character any more and canonically all the raids and boss fights after that were done by other players, and mine (canonically even!) just fantasized about it pretending I was there. Even in the very last fight against the Witness, canonically, I was just one of hundreds of thousands in a faceless army that defeated it together.