Possession

He had never considered he'd come home to Atreus attenpting to sleep with a mortal, nonetheless a man.

Needless to say, at the sound of a breathy moan, insticts took over. Though fatherly insticts they were most certainly not.

Kratos had never felt such a blinding rage in all his years as he held this, this- pathetic mortal. 

He was going to make this begging boy regret ever laying eyes on Atreus.

...

It was quicker than he'd like. The man didnt deserve such a mercy for his attempt at tainting his boy.

Kratos sighs, chest heaving as he rubbed his face, blood smearing upon it. He looks through his fingers at the door that stood between him and his son. 

His son that must be punished. 

He doesn't cast a glance to the corpse that lay beside his feet, bloodied and mangled past recognition, as he walked to the oak door. He'd dispose of him later so Atreus would be spared of such an image. 

So he'd never see him again.