How to remove failed macports software?
Solution 1:
Try cleaning all the packages first.
sudo port clean --all all
You can also try
sudo port uninstall inactive
If those fail, add the -f flag to force the operation.
You might also be successful using.
sudo port -f install gimp
If you don't need the latest version, download the binary from the gimp website or try the native version http://gimp-app.sourceforge.net
If you have not installed any gtk2 dependents yer, you can try installing the native (non X11) version using the +quartz flag.