Got this from gamefaqs
SILENT HILL 3 ENDING REQUIREMENTS
"NORMAL" ENDING
Basically this is what you\'ll get for following through on the game as normal.
The only reason you won\'t get this is if you follow the information as it is
noted below (and this could happen by accident as well if you hadn\'t known)
although it\'s not always easy for people to get anything BUT the normal
ending of the game.
"POSSESSED" ENDING
This ending changes the final scene of the game that takes place. To receive
this ending you need to do the following:
- Kill as many enemies as you can. This doesn\'t mean everything, but a large
number - normally over 100 - will do.
- Be damaged a lot and run around needing health a lot. At the end your total
damage is shown in points and needs to be over 2000 (although if you get
over 4000 you\'re more than likely to get this ending).
- Forgive in the confessional. When you get to the church and go inside,
you\'ll have the option to forgive or not say anything. Forgive and you\'ll be
putting the final nail in the "Possessed" ending.
To not get this ending, avoid the previous three steps (kill only what you
need to, avoid damage and heal when required, and don\'t say anything or even
totally avoid the confessional section.
"REVENGE" UFO ENDING
This ending was discussed at the correct section of the game, which is when
you arrive home to the Daisy Villa Apartments. At this point of the game you
can earn a bonus ending, but only if you\'ve met the right requirements to do
so.
This involves the Heather Beam which you may have earned, or may not yet have
earned. But either way you\'ll need to know these requirements when you start a
"Extra New Game", rather than just when you arrive at the apartments to get
the ending. To get the Heather Beam either check at the start of the guide or
just down below at the full listing of secrets.
You need to use the Heather Beam to kill more than 30 enemies. You can\'t use
any other weapons except the Heather Beam, and even killing them by kicking
them will count against this ending - the kill count for shooting and
fighting has to be 0 and this is the only way to do it.
When you enter the Apartment the "Revenge" ending will take place.