One thing that gives me great peace of mind as a Christian is the specific New Testament (and implied Old Testament) teaching of judgement...for every single human being. Every country has its serious injustices...murderers who get away with it....rapists never caught...or sometimes, whole races who rise up and commit genocide (or democide, actualy the proper general term for the purposeful killing of entire populations civilians.) No matter how dilligent and competant a justice system is...some will get away with it--and on the world stage, that means thousands who've murdered innocents, go free and prosper. A terrible miscarriage of justice, for sure, however, when all is said and done, its a great comfort to know there is a Judge, who will set things right.
America's (and the UK's) system of innnocent until proven guilty foundational principle is based on that premise...that we should do all we can to punish wrong doers, but must assume innocence, as it is worse to punish an innocent man than to miss punishing a guilty one....because, even after we mess up....justice will prevail in the universe.
The most concentrated killing ever recorded though was in our lifetime....not long ago. In 1994 between April and June, up to ONE MILLION of the Tutsi tribe were slaughtered (literally, mostly by machete) by the majority Hutu tribe in Rwanda. That's nearly 300,000 a month. Even the Nazis were never so "efficient"... and the UN (and Bill Clinton) did not try to stop it. More that 10% of the country was hacked to death.
There are probably over 100,000 perpetrators of the Rwandan butchery....and most of these will never see punishment--to even try to prosecute all would be impossible practically and yes, it would destroy those who remain in that country. Prosecutors have sought out the ringleaders of the butchers...but that's the best they can do.
Yet the untold story is the amount of reconciliation that has occured....not led by UN peacekeepers, but by the churches of that land. Repentent murderers worship side by side now with those whose families they wiped out. It's almost beyond understanding how such healing can occur. I'm not saying its good policy to let repentent murderers off the hook--but with a situation like Rwanda, the numbers of people involved were so vast...it would take another genocide to punish them--something no one wants to occur. That God will hold people to account...and that the blood of Jesus by the power of the Holy Spirit can forgive and even turn murderers into godly persons is truly incredible.