I Did What I Had to Do/Analysis
Sometimes the character is so proud of the necessary toughness to make the sacrifice that he makes a Stupid Sacrifice just to show that he is really that tough-minded and hard-boiled, as opposed to childish and antiquated objections. Other characters may, quite reasonably, conclude that getting around the problem would have been possible—even simple and straightforward—but the character just wanted to show how tough he was, or perhaps was simply too lazy to find the better solution.
In contrast, it can often be an example when a hero will steadfastly refuse to Do What He Had To Do, no matter how clear-cut the case. When saving many people will cause a small number of people to die, many people would favor the utilitarian approach that saves as much life as possible, even if it means "dirtying their hands" because they would see refusal to take direct responsibility over the deaths as short-sighted or morally cowardly.
Whether or not a character can get away with this depends a great deal on where their world is on the Sliding Scale of Cynicism Versus Idealism. Shooting the Zombie Infectee is almost always considered justified. A hero who refuses to kill a villain who is known to kill innocent people for pleasure, has stated no intent to stop killing, and is completely and utterly irredeemable, and instead throws them back into a Cardboard Prison time and time again (even if they have no problem killing their underlings or just leaving them to die,) simply enables further murder and bloodshed, and is lawful stupidity verging on a moral flaw once you think about it for a while. When the author acknowledges this, expect a Poisonous Friend to Shoot the Dog, if not a Big Damn Villains moment, which only seems to prove that the hero's high-minded ideals just do not work. In some cases, as with the Advance Wars example below, this is especially jarring, because The Hero has indirectly caused deaths before, and knows that deaths will result from his inaction, but refuses to take responsibility for the final step of doing the dirty work himself. If the author steadfastly refuses to budge from the "idealism" side of the scale, however, anyone who tries this will see his plan dramatically backfire.
When the roles are reversed, the line is usually You Did the Right Thing. Contrast Must Make Amends, Big Damn Villains, and My God, What Have I Done?. May result in Death By Pragmatism and Cradling Your Kill. If your ruthless plan succeeds and actually does bring about the greater good you're aiming for, that's The Extremist Was Right.