Answer:
Cruel is defined as:
"Disposed to inflict pain or suffering : devoid of humane feelings"
Mean is defined as:
"Being deliberately unkind"
That is to say that a cruel person is one who evades human emotions to inflict harm on others, on the other hand a mean person is the opposite of kind, someone who is not characterized by being sympathetic. Comparing these two differences, logically, being cruel is considered to be worse than being mean.