I am a major supporter of the Enclave in all Fallout games (with the exception of Fallout New Vegas, I only liked Orion Moreno), so I would have to say "Very Evil" by the Fallout karma rating systems. I never play as anything else. I usually try to avoid wastelanders as much as possible, but if I do become within range, I fire on sight.
I had modified the game via GECK however to give me Good karma for administering the FEV to the purifier (correcting a small mistake by the developers, obeying your President's orders should always be considered the good choice).
Here is a small list of things I always do:
-Detonate the mutie town of Megaton via the request of classy dressing mutie scumbag. Then I exterminate the mutants residing in Tenpenny Tower.
-Exterminate residents of Big Town.
-Exterminate residents of Rivet City (with the exception of main quest characters, father is still indeed human anyway, though he's a mutie lover, so he is still on their level).
-Exterminate residents of Paradise Falls (sometimes sparing the younger mutant scum).
-Exterminate residents of the Citadel (when access is given) - later I destroy it via Broken Steel DLC.
-Exterminate all residents of Republic of Dave, reload game and exterminate them again, just in case.
-Terminate Harold in the Oasis, then exterminate residents in the Oasis.
-Exterminate savages of Evergreen Mills, including the mutant captives.
-Seize Fort Independence.
-Seize the Jefferson Memorial.
-Exterminate all life in Dukov's place.
-Seize Lincoln Memorial, after returning head and complying with mutant slaves, then exterminating them.
-Seize Washington Monument, killing any Brotherhood of Steel around it.
-Sterilize the area around the Mall.
-Sterilize Mutie Dog and eliminate all surrounding organisms near Galaxy News Radio.
-Comply with all U.S. President's commands.
-Refuse to turn over activation codes to Colonel Autumn (as he would both kill you and turn against the President).
Many more, but I think I would have to say Exterminate/Seize "insert location/area" here.
God Bless the Enclave, God Bless the United States of America.