Love the man who seeks his own demise, for he is the transition to the Übermensch
So I guess you don't need "humanity" in the sentence. So, with the words in your sentence, it would go like this:
Liebe den Mensch, der seinen eigenen Untergang will, weil er der Ubergang zu den Ubermensch ist.
I believe it's like that. I'm not too strong in German grammar...