An interesting thing about William Nelson - his uncle was Alexander Doniphan, the lawyer/soldier/frontiersman who saved Mormor leader Joseph Smith from being executed without a trial and figured prominently in the Mormon Wars fighting against the same man - he has quite an illustrious legacy in Western history. The Toughest Man South of the Picket Wire was based on him - Tom Doniphon/John Wayne in The Man Who Shot Liberty Valance.
Nelson was one of those commanders killed so early in the war he didn't have time to prove whether he was going to be good or not. He was at least as tough as his uncle, very much a bull and, no, not liked by his men. At that time in the war, most officers were elected by their men...Nelson might not have won! He'd started his career as a sailor, Annapolis graduate, and had a great deal of experience in a different area commanding a different type. How he came to be killed - he called Jefferson C Davis a puppy! Well...them's fightin' words. Davis got a gun and shot Nelson knowing he was wounded and unarmed, but also that he wasn't going to kill him any other way. As noted, the remarkable Gov Morton put in a good word for Davis, Lincoln needed officers and there it went. Apparently, at the time, killing someone who insulted you in this manner was not considered cowardly, as long as family honor was cleared!
My main problem, of several, with Jefferson C Davis comes many years after the Civil War - he came to California and finished the Modoc War...and the Modocs!