Quote Originally Posted by weelilmatt
try:
Wowhead.com
Database>Quest>Create a Filter

Search "kill" then check extend search

the rest is up to you:]
Great tip yes, just tried it.... However, might be better to search for "slain", as all kill quests seem to have in the description somewhere X of Y slain.

Some I suspect may not mention the word kill, but instead slay, terminate, extinguish etc.