I wrote a Tampermonkey script which more or less was a true 'automate someone out of a job' situation, except it didn't do that at all; it freed up 20+ hours a week that someone had to sit there and do this awful manual thing with vendor portals, csv's, and spreadsheets.

I haven't worked at that job for almost a decade, and last I heard it's continued being used with only a small amount of maintenance.

That's the most compliments I've ever gotten for any software I've ever written and it had very real human impact.