How to find and delete both original and duplicate from a list of entries

I need to get two computers to an identical state, so I have created a software list of each and in a CALC I have a coloured font for one and black for the other list. I have put both lists in one column of CALC and then sorted ascending. What I need to do now is to find and delete any duplicates and delete both original and duplicate entries. This will leave me with a list of packages that are on either machine, but not both. The colour of the font will distinguish the machine. There are approximately 4000 packages in each machie, so the list in column A is around 8000 lines, a prodigious task to tackle in a manual way. What tools can I use to achieve the desired result?

There’s a variant version of your question in a previous Q&A. There are some good solutions posted in that thread that I think will work for you – if you still have the original distinct lists available! (I hope you saved them individually before merging them.)

The available solutions depend in part on the platform/OS you’re using, so could you add that to your question, in case someone has a better idea for you? If you’re on some flavour of Linux, for example, then cat solution that @qubit1 gives is superb.