I RP this toon as Chaotic Good so I definitely think it’s more than possible. However with an undead character I think you need to keep them forever spooky.
In the case of the Forsaken they tend to crave the flesh of the living. Which makes sense as it can heal them. Death Knights also have an urge to feast off the pain and suffering of others. Now in most settings this would skew them to at best neutral. But in Warcraft there’s really no shortage of chaotic evil humanoids who want to ruin all of creation. The Naga and N’Zoth Cultists come to mind as recent examples.
In Benedikt’s case I write him as a Cleric and Alchemist who’s a generally nice person who believes firmly he’s a duty to heal. However he’s also still a creature of darkness with macabre predatory urges. This isn’t usually a problem - humanoid meat isn’t hard to come by just wander by a shore until you find murlocs - but some are unnerved by his tendency to ‘recycle’ enemies slain on the battlefield.
For a Death Knight Guardian type I could picture someone who is noble and but gets a touch sadistic with those theyve to protect people from. Maybe twisting the blade inside the wound of a dying enemy to really savor their suffering. That might sound cruel- because it is - but that’s how undeath works. They were instilled with terrible, unnatural feeding methods because the Lich King designed them to be inhuman monstrosities. They can’t help that aspect of their nature anymore than the living can fight their need to breathe. But they can chose to be cruel or vicious only to those who’ve earned it.