It depends who it is being justified to.
If I were to kill a thousand people to save one life, then you might think the ends cannot justify the means, no matter who the person was.
However, if I love that person deeply, then I might disagree.
That doesn't make it right, but one person thinks the end justifies this action.
However, if you were to kill one person to save a thousand, that may be considered justified by the majority of people.
The person that had to die would probably disagree, as would their family.
My point is that the ends can always justify the means. It just depends on where you are standing.