Civilization – How to achieve the ‘Know Thy Enethe ‘ achievement in CIV V

From the multiplayer menu, choose "Custom Games", Create Game, and in the game lobby, "Add AI".

"Evenly matched" in this case means you and the opponent AI have the same handicap percentage specified.

From the civfanatics forum:

Khaaan! requires an outright loss through both score and lack of conquests. If you want the achievement, easiest is to give all your cities away to a remaining AI one turn before the end of the scenario, then press end turn.