I'm not disagreeing with you, Neither am I arguing Slade Wilson is a wolverine-type figure with a secret heart of gold. My argument is that the names we are mentioning here - Kingpin, Magneto, Deathstroke, The Punisher, Kraven, etc, are more than just one-dimensional psychotic killers without any code of personal conduct or self-discipline. What you have to recognise is the difference between the extremes of what makes some villains more enduring and popular than many many others around them.
Deathstroke began life as a mercenary figure who's professionalism and expertise made him one of the most respected and feared assassins in the world. One of out very first sights of him is of him and his man-servant Wintergreen discussing business ventures while looking down from opulent surroundings in some city penthouse, and that helps set the style and tone of the character from thereon.
The term "anti-hero" only came to possibly apply to him much later, after his 1990s series and before Geoff Johns' Teen Titans revival. As careful as Marv Wolfman was in handling Deathstroke's violence and who he was targeting in that 90s series you are so critical of the fact is he was still the same assassin he was when we met him, still accepting contracts and killing people.
The key point is however that like Frank Castle's victims the people he was targeting arguably deserved what they got, and like Castle the publisher was being very careful in ensuring that. The point I make comes down to image and protecting that image. If Deathsroke or The Punisher were shown early on killing pedestrians through sheer carelessness and indifference then neither would have ever earned or deserved the fascination and support they gained from the readership... it is their code of conduct and why they do what they do that made these characters mentioned here so interesting to follow and study historically.
Really nice comparison between DS and the Punisher, as both will target and kill without any qualms those to them worthy to die, but will not jsut target others for no reason...