Turning the lights back on...

[I-K-E]

turning on a power station .... most modern stations are build so an operator can't screw it up

BUT if how would you get the fuel to them as them need a hell of a lot to feed the current grid?

With a massive event there is not going to be commercial coal mines on the other side of the earth shipping coal across the oceans. And that is the same for any of the things that you would consider turning back on.

Personally I'd be looking at clean water and sanitation but build it up from what was left. Basic medical would be important too and it would be interesting to get some sort of basic drug processing up and running. But this is assuming that survivors start coming together so it would be happening a good long while after the chaos that reduces the population and in this senario you'll be looking at specialisation so it would need to be a working community and a working barter or cash system .

Basic electricity yes but only small scale and only for important things and that would not be first.