In Judaism, the only person who can actually forgive anything – is the victim.
So you see, we cannot ‘forgive’ those who perpetrated the Holocaust. It is outside our power to do so.
And – to give a frank answer – even if Judaism agreed with forgiving on behalf of the victim, I personally would not and could not forgive those who slaughtered six million Jews (including one million children) and millions of NON Jews also.
Some things are, simply, beyond forgiveness.