Good guys?
In 40K (Warhammer: 40,000)?
Heh, let me stop you right there, kid. If what you're looking for is some "clean cut" morality within factions or races, well best keep on lookin' cuz ya ain't gonna find it here.

In the 41st Millennium, you do what you have to to survive, end of story.
It's considered "Grimdark" for a reason ya know. Equal parts grim and dark.