1) Bad-mouther 2) Badmouther 3) Belittler 4) Bully, by nature 5) Bully, often 6) Degrader 7) Degrading sort 8) Humbler 9) One belittling 10) One putting others down 11) One who belittles 12) One who humiliates 13) One who s degrading 14) Person degrading 15) Put-down artist 16) Shame is his game 
• (n.) He who, or that which, abases.
A·bas'er (ȧ*bās'ẽr) noun He who, or that which, abases.