Is Richard III a beast or a human?
Definitely a human. Otherwise, it surely wouldn't be a tragedy. And I don't think Shakespeare believed that anyone was born bad. That'd just be dramatically boring.
Right from the word go, Shakespeare emphasises that Gloucester is someone who would like to be involved with everyone else, but cannot because of his disability:
But I, that am not shap'd for sportive tricks...
I, that am curtail'd of this fair proportion,
Cheated of feature by dissembling nature,
Deform'd, unfinish'd, sent before my time
Into this breathing world scarce half made up...
In war, Richard can win respect by fighting. In peacetime, he cannot be included in the dancing, lovemaking and general merriment:
Why, I, in this weak piping time of peace,
Have no delight to pass away the time
Unless to spy my shadow in the sun,
And descant on mine own deformity.
Richard's disability means that he is left out of peacetime society. And his reaction to it is logical:
And therefore - since I cannot prove a lover,
To entertain these fair well-spoken days -
I am determined to prove a villain...
Richard goes on to do horrible things, of course. But what you think of him depends on how you read "determined" in that quote. Is he pre-determined (by God) to be a villain? Or is he simply determined (i.e. resolved) to be bad? Does his disability (which he was born with) justify - to any extent - his behaviour?
You can argue both ways. But pity him or hate him, Richard is a human, and not just a beastly baddie.