"Unaligned" (which is basically a type of true neutral) could also apply. He's a just a guy who tries to get through life. He'll be nice when he can but is perfectly willing to do bad if that's what it takes.
But, he does have a code he lives by. It's just that Conan decides what is "right" and what is "wrong", not society.
Yeah, well, actually we don't know that. Howard never wrote anything about raping women or murdering children, unless it was folks like the Picts or something, whom Conan despised. Howard's stories weren't meant to be realistic. While his men were often savage pirates, brigands and raiders--from time to time--Conan himself was always seen in opposition to that kind of behavior, and Howard certainly never said that it happened on his watch.
I think your point would have more weight if we were just talking about one group or marauders. But, Conan lead the Red Brotherhood, on two seas (the Great Western Ocean and the Vilayet), the Kozaki, the Zuagir, and his own Free Company--not to mention the armies of a few southern kingdoms (as with Black Colossus--and depending on whether you stick primarily with Howard or also include pastiches/comics).
It's hard to believe that all of these groups were reigned in by Conan's command and ceased the darker aspects of raiding, plundering, pirating, and marauding.