My oh shit moment was Opus 4.6 before it got nerfed.
It helped me refactor my old app. Something I always wanted to do, but didn't have time/mental capacity to do in a short space of time.
I wrote a short prompt, explaining how I want it to look like and which files it should go through. It asked me a few clarifications and then basically one shotted it.
Everything compiled and worked. Now my internal app is much much easier to extend and test.
I tried few more things like that and spent like £5k in the tokens in those two weeks.
Then it got nerfed and never worked like that again.
Now I don't use AI, because it is shite again. Even Opus 4.8.