S/he is cruel to a weaker person (5)
I believe the answer is:
bully
(Other definitions for bully that I've seen before include "One persecuting weaker person" , "excellent" , "Intimidating person" , "Flashman, say" , "Playground thug" .)
I believe the answer is:
bully
(Other definitions for bully that I've seen before include "One persecuting weaker person" , "excellent" , "Intimidating person" , "Flashman, say" , "Playground thug" .)