The dogs in Penumbra: Overture can be killed with just the pickaxe - it's a bit akward due to the controls but not too hard. Not sure about the spiders, but they are only a small part. The giant worm is unkillable afaik but it's only there for one chase sequence.
Definitely takes the edge off the horror aspect when you figure that out. But then again, I like both the Penumbra series, Amnesia: A Machine for Pigs and SOMA more as exploration/puzzle games with a scary atmosphere than for the actual horror aspect.
I think the people who enjoyed the games were the ones that could get sucked into that mental model early and didn't want to die in game.