what was the hardest thing you created?

Question: what was the hardest thing you created?
- Keywords:
  challenge,
  work
Asked by itssimplyjustme to Tom, COLFlight, Beth on 14 Oct 2015. This question was also asked by supersonic7c, Sam.
- Columbus Flight Directors answered on 14 Oct 2015:
  
  Sergio:
  Hi there!
  I’m not sure what you meant with “hardest”. In our job, we don#t really create any hardware; we use the hardware that has been built by others and we create good and efficient ways of using it.
  
  But I can tell you what was the hardest thing I broke! When the German astronaut Alex Gerst was on the space station, he once broke a screw while trying to remove it. I was directing him during the operations when this happened, the screw was jammed and I told him to pull harder. So it was also my fault if the screw broke…
  And then we had to work really hard to find in short time a way to remove the part that was jammed in the hole. We created some instructions for Alex to saw off the broken bolt, he did it and we solved the problem!
  
  According to NASA, something like this had never been done before in space. So now I can say that I participated to the first ever cutting of a broken bolt in space! 🙂

Question: what was the hardest thing you created?