I have level 14/15/16/18 saves of a very evil character, high Sneak, Unarmed and Big guns skill. I don't quite remember which stage of the main quest she's at. I also have a level 22 save of a neutral character with high Sneak, Explosives and Speech skill. If you don't mind the Impartial Mediation perk being rendered useless, you can go ahead and lower the karma. His current objective in the main quest is to retrieve the GECK.