The Chosen One must kill Metzger, the leader of the Slaver's Guild. While there will be 1000 XP added immediately after killing him, it should be kept in mind that all the slavers in his room and in the rooms around it will retaliate in response.
The Chosen One can then go and tell Becky that Metzger is dead. Becky will then offer $1000. If the reward is refused, +50 karma is given instead.
Killing Metzger prevents the player from completing any of Lara's quests.
Many residents of the holes will comment on the death of Metzger, mostly in a positive way.