The time that I felt most like a Dev badass was when I had introduced an E2E test framework and added a bunch of helper classes to it so that our QA team could pick it up and write automated tests for the manual tests they had been doing for years.

Sure, the whole department got laid off after that because we had gotten a new CTO and all of my work was essentially for naught, but it made a lot of people enjoy showing up to work for the first time in a long time, and that was what mattered most to me