Yeah but he's always glaring like that the throughout the whole series. I wonder how you felt when he was murdering the gods especially poseidon and hermes, those were gnarly af!

What can I say... I wasn't really bothered by killing Poseidon, nor Hermes. Sure, they were grisly and graphic, but I never felt anything while doing that. Neither did, I feel, Kratos, apart from the usual rage that he feels pretty much all the time.
That glare though... he just lost something he actually felt passionate about... a surrogate daughter. And to figure out that it was all for nothing and getting mocked for it by his father(whom he hated before and whom was at least partly responsible for Pandora's death, at least in my view)... yeah. That glare doesn't say, I'm going to kill you. That's the glare that says, I'm going to kill you, rip off your ****** head, **** the hole that's left and ****** on your cooling corpse. Then, I'm going to resurrect you(somehow), do it all again, only make it more painful this time.
And you know he's totally gonna do it. Because this time, it's personal.