I just thought I should sum up my own thoughts about this, all together with what many of you allready have discussed:
There are several details suggesting that Travis
did some horrible acts he didn't remember and/or know about before.
The facts are:
As for the first: Remember how we even got that ending: By killing atleast 200 monsters.
Second: Remember when Heather met Vincent in the Library in SH3? Vincent pointed out:
"They look like MONSTERS to you?!?".
Third: If you read the explanation to the accolade "The Butcher", which you get along with the bad ending, it tells that
"Travis comes to a disturbing realization", which clearly encourages us to think outside the simple idea of Travis just being held prisoner by the cult.
Fourth: Back again to those voices in the bad ending,
stating he is killing someone.
Are these voices old memories coming back to him, are they hallucinations or are they just repeated from the reality of what he just did in Silent Hill during this last visit?
Fifth: The accolade for accomplishing the bad ending
is called "The Butcher" and in the same ending we see Travis switch between being just Travis and between being the butcher in a couple of fast frames. This is being shown not when he's being tied up on the bed, but somewhere else, sitting.
Once again: Memories, hallucinations or something else?
About the thing with Silent Hill bringing people who have issues to deal with, I like this guys thought:
If you apply that logic to the endings, the good ending would then suggest he dealt with his past and his dark side. Also, that he is moving on and starting over. The bad might suggest that he's learned nothing from his journey through SH and will become the very thing he was fighting.
Which, I assume, would be the butcher. And I agree on that part. If so, I also keep in mind that just about everything in Silent Hill is to be interpreted metaphorically. Travis becoming the butcher doesn't nessecarily meen he's physically being transformed into an allready existing being, but rather that he is being transformed into something dark from his subconcious, just like most other people in Silent Hill allready have been.
Just when I've gotten used to "today" it's suddenly "tomorrow"...