One putting others down

• Bully, often
• Shame is his game
• One who degrades
• Bully, by nature
• Belittling one
• One who humiliates
• Degrading sort
• Put-down artist

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
Abaser \A*bas"er\ ([.a]*b[=a]s"[~e]r), n. He who, or that which, abases.