One need look no further back in history than the Nazis- there are documented reports of young Germans whose choice was kill X people or else. Those that chose not to slaughter Jews (or Gypsies, or homosexuals, or whomever the designated victims were to be that day) were killed, right alongside the people they refused to kill.
Since we started discussing
Evil in the context of raising Undead, we are (I guess) talking about
Evil in the D&D Game (or in the Fantasy Fiction that inspired the Game) where
Good and
Evil (and morality in general) are tangible forces that can be defined, embraced or opposed, etc.., etc.. .
If you include discussion of Terrorists, Serial Killers or the Genocide in Germany or the Sudan, it would stand to argue if
Good or
Evil exist in the real world in the literal sense that they do in fantasy games or fiction.
I'll leave my opinion on this out of it, as much as it itches me to comment on some of the examples mentioned above. If you want to discuss
Good &
Evil in the Real World, start a new threat. In this thread it is just derailing the topic at hand.
It may be worth killing 1000 innocents to save the scientist who is within reach of finding a cure for cancer. Similarly, it may be equally worth sacrificing an innocent so that 1000 other innocents escape to spread word to the world of the genocide in Sudan.
If some action like the one mentioned above is "
worth it", or not has nothing to do with the question on if it's evil or not.
As most fantasy fictions are morality tales as often as not, I would argue that the prospect of greater gain is almost always the lure of
Evil, while the righteous path seems ever the one without more tangible gain, less tangible risks, the one with far less chances of sucess in general.
As mentioned with the Raise Undead example above. The fact that you'd consider corpses (or slaves, or whatever) to fight your fights for you is just as good an indication for your evil disposition, as is the act of raising dead itself.
The good guys wouldn't resort to dishonorable tactics (raising dead, taking hostages, attacking without challenge, etc..) just to improve their chances of success, or if they do, they know that their acts are not good.. likely evil.
Thats why an "the end justify the means"-attitude is (in classical fantasy fiction & games, which the standard D&D builds on) the mark of evil.
Your milage in real life may differ...