XDMG shows the damage of the person you are killing in the chat bar. There is a CSS version that shows it as a message, but HL2DM doesn't support them.
Installation
Put es_xdmghl2.txt in addons/eventscripts/xdmghl2.
Version Notes For 1.4
Updated on: 2010-02-08 00:47:36 EST by pand3mic (View Zip Contents)
Added A kill message and Plays a little sound!
Upload Addon