SciFi and Fantasy Art: Commissioner's etiquette

The story behind this one was a comrade (I can't call him a friend even though I didn't realize until later what a waste of O2 he was) asked me to do a picture for him, and I agreed. After working on it for a few weeks and several exchanges back and forth, he mentioned that if he didn't like the end result, he'd just change it himself. At this point I slammed on the brakes, informed him that I withheld all the rights to my art, especially the free stuff, and he was not going to do a damned thing to my work. He responded that since the character was his, the rights were as well. (I love it how some idiots think they can play copyright lawyer.) After a long argument, and my then-fading faith in this person completely gone, I cut him off entirely, and Rhynne here is still unfinished. This portrait is barely half-finished, and it's been sitting in my hard drive for a couple years.