Does each person have a particular True Nature, according to Buddhism? I know that there is what is described as universal True Nature - aspects common to everyone. I know about Karma, which can be seen as how beings have tendencies even from birth (which otherwise has no explanation that I can see). This question is whether each person (regardless how you think they exist or not) has a particular set of characteristics that are theirs to express in living their full potential? 

Buddhism is sometimes accused of being nihilistic in the way that it seems to leave no reason for people to function when they overcome ignorance and realize the truths. This is your chance to explain, using references, that no, every person is a valid and necessary part of the complex web of Experience, not just a wrinkle that escaped temporarily from The Void.
To the best of my knowledge Essentialism is not a part of any school of Buddhism. Essentialism deals with metaphysical essentialism, and is essentially on the opposite end of the spectrum from emptiness/sunyata, which might be refereed to by some as Metaphysical anti-realism. However I have not met many Buddhists that want to jump into that classification. Taoists love it though. The Buddhists will assert that there is an Ultimate truth, and so can never truely be metaphysical anti-realists. At least not in the most extreme case of the view. They do show some grey areas from time to time.  

A quick dirty and brief summery of metaphysical anti-realism is that there is no "Truth"
but some views are more true than others. It is found in various places within eastern philosophy.

Also Buddhism is not nihilistic, never do they throw up their hands and say, nothing matters do whatever you want. The only term with nihilism in it that might come close to paralleling with the Buddhist worldview that I can think of is Mereological nihilism.