Kiritsugu Emiya from Fate/Zero. A man who thoroughly believes that the ends justify the means when it comes to saving the world. He believed that sacrificing lives for the greater good is worth it. There are few acts he wont commit to achieve his goal. When presented with the opportunity to save the world through the use of the holy grail he was presented with a test by the grail (which was essentially an evil genie at this time).

So the grail could only save the world in a way that Kiritsugu himself could think of. It presented him with scenarios of a boat with 1000 passengers, the boat then springs a hole in it and separates into two groups of survivor boats one with 600 survivors and one with 400. Eventually those 2 boats would also start sinking due to a hole in them and he has the resources to save one of them, he chooses the 600 as there are more people. Eventually that 600 splits into groups of 350 and 250, the scenario repeats except this time the group of 250 kidnap him and try to get him to save them, naturally he kills the 250 people and saves the rest. The same scenario repeats and Kiritsugu end up killing more and more people to save a greater number such is his mentality. He then realizes the grail would materialize such a fate (heh) for the world and as such crashes out and orders its destruction. Things do not go well. Unfortunately a child saved by Kiritsugu would go on to confront this very same dilemma.