Guccifer is the person you face off in the 4th tier. His boss robot is Myrmillo.
He has the attitude of a rebel teen and is arrogant beyond belief and malicious. He lives to destroy and humiliate his opponents. He's petty, selfish, and only slightly charming when being cocky.
Sometime before the last circuit, he says that he is a junior hacker.
Defeating the Myrmillo boss will give you a Forty IV card.