As far as I have gathered from the books, wandless magic can be performed by children of age eleven and above when they are in an emotional, for want of a better word, crisis.
What I mean is, for instance Harry blew up Aunt Marge without a wand when he was in a rage.
So, assuming that adults too can perform wandless magic, to what extent can they utilize their powers in this field? Does their emotional state matter too? In case of powerful wizards like Lord Voldemort, can he perform such magic to a level not attained by any other wizard or witch?