I haven't played SH3 so no idea what she was fighting. If it was "God" again, like at the end of SH1, it was God. God is not Samael.
Valtiel is the "Red God". I believe SH3 mentions a Red God and a Yellow God or we see them in a portrait. It is supposed to be the guardian of God and its duty ts to bring about God coming to life. That's why it was put in Walter Sullivan from SH4 because Walter was going to bring God onto Earth.
I'm no expert on SH demonology but I suggest visiting Silent Hill Heaven. It has a great deal of info there on the subject.
Okay I'm here to help end this debate if possible. For one PH is an entity that's sole purpose is to cause its victim repent for its sins. There for it will take on a form that is unbeatable to it's opponent, be it strength or whatever. So to have MC fight an actual brawl against PH is impossible as PH is invincible, he is a god after all. What I'm saying is MC can't win with his physical abilities, only by realizing his sins and repenting can he win. It's just the way it is.
Master Chief and Pyramid Head
Alright, so I've read the top half of all the comments put down, and it made me a bit curious. So I decided to go to Halo Nation and the Silent Hill Wiki and post down what they say.
(According to Halo Nations)
Master Chief was trained from the age of seven to become one of the ultimate super soldiers, and he is one of the best, who also lost all of his friends and comrades. He was the number one (or second if Noble Six was first) choice for Cortana, while Noble Six was chosen to be the courier to bringing her to him. This happened because she saw him as the luckiest soldier alive. He held the best leadership out of most of them. He has gone through the fall of reach, the defense of earth and humanity, the flood infestation on installation 04, flew through space and detonated a covenant bomb on it's own super carrier, destroyed two and a partially built halos, fought through the arc, going through flood and covenant soldiers alike, was lost in space for a few years, and fought one of the deadliest Prometheans before he could attack earth (or already did). He lost many that he cared for, and was slowly beginning to feel for each. (I don't know if this is true) when chief was forced through evolution by the Librarian, I am guessing that gave him back some of his emotions, which might explain him crying when losing Cortana.
(According to Silent Hill Wiki)
Pyramid Head, also known as the Red Pyramid Thing, is a monster (and in two cases, a duo of monsters) appearing in Silent Hill 2 as arguably the main antagonist. In Silent Hill: Homecoming, a monster known as the Bogeyman closely resembles Pyramid Head, which furthers the theory that he has multiple incarnations and is frequently associated with feelings of intense remorse. If you complete Silent Hill Homecoming with only making evil choices, it shows two bogeymen playing a pyramid helmet on Alex Shephard's head, making him one of the many.
(Copied and pasted by Silent Hill Wiki)
The Pyramid Heads serve as a manifestation of James's unfulfilled desire for punishment for Mary Shepherd-Sunderland's death. They could also represent the darker part of James's personality. Pyramid Head shows this by committing brutal acts that James has done or has thought about doing, such as murder, and his constant twitching could symbolize James's needs, emotions, and fears.
The Valtiel sect, which revered the angel Valtiel as being closest to God, wore red hoods and white robes in homage to him and acted as executioners. Pyramid Head's helmet bears a resemblance to the red hoods, referencing his role as an "executioner" of sorts. However, the helmet is also designed to appear extremely uncomfortable, acting as a torture device as well as a symbol of authority.
So, it's hard for me to tell if Pyramid Head is real or fake, but he is supposed to closely resemble James Sunderland, and is an executioner. He only arrives through guilt, or the such. If Chief is going through these things, then a Pyramid Head (possibly a different, and highly stronger character) will show up with much resemblance to the Chief.
Don't believe me? Check up the wiki and Halo Nation. And hell, in Silent Hill Origins, the Butcher takes Pyramid Head's place for Travis Grady.