To uninstall mlton-runtime-native just follow these instructions.
/ubuntu/trusty/universe///install/index.html Optimizing compiler for Standard ML - native runtime libraries Ubuntu 14.04 LTS universe/devel 20100608-5.1
sudo apt-get remove mlton-runtime-native
Which will remove just the mlton-runtime-native package itself.
sudo apt-get remove --auto-remove mlton-runtime-native
This will remove the mlton-runtime-native package and any other dependant packages which are no longer needed.
If you also want to delete your local/config files for mlton-runtime-native then this will work.
sudo apt-get purge mlton-runtime-native
Or similarly, like this mlton-runtime-native
sudo apt-get purge --auto-remove mlton-runtime-native
|Description||Optimizing compiler for Standard ML - native runtime libraries|