Antagonists ("opposing force") in the Silent Hill series.
Please note that this category is for human characters, not monsters. This isn't to say that monsters aren't antagonists since they are in a way, but if every monster is considered one, then this category would be crowded. Humanoid monsters such as Pyramid Head will not count.
Some monsters which are based on real humans or have any antagonistic role in the series as a human will be included (such as Leonard Wolf who tries to kill Heather). Also, this only includes antagonists which are antagonist to the protagonist. For example, Richard Braintree has been antagonistic to Walter and the other residents of the apartment building, but not to Henry. Richard is antagonist to Henry as a ghost, but he is a monster at this point, and humanoid monsters do not necessarily count. The difference between Leonard and Richard is that Leonard chooses to attack Heather of his own will, while Richard is the victim of being a ghost.
Please note that antagonists do not necessarily have to be evil or a villain; Michael Kaufmann in Shattered Memories is an antagonist trying to help, but still opposes their client. All "antagonist" means is that they have opposed the protagonist at some point (Alessa opposes Harry and Travis). Silent Hill is complex and isn't black-and-white on how it handles its antagonists. For example, it is debatable if Vincent Smith is an antagonist. However, if a character attempts to oppose/attack the protagonist at some point to a notable extent (such as Maria), they will be included.