Getting a list of outdated versions with Python
Since everything is printed in order, the "obsolete" ones are all but the last version for the first word. That's tricky. But if we looked at the text backwards, we're printing all but the first one. 

And that's easy with awk:

awk '!($1 in seen){print }{seen[$1] = 1}'


And then just invert the input twice:

run_your_version_cmd_here | tac | awk '$1 not in seen{print }{seen[$1] = 1}' | tac