Kratos is incredibly powerful, but it's hard to say if he's the absolute strongest. Different fictional universes have their own mightiest characters, and it depends on various factors like their powers, skills, and the context of their stories.
The story of Kratos is complex and compelling. He was once a servant of the Greek gods but was betrayed and wronged, leading him on a violent path. As the series progresses, he grapples with his actions and tries to find a way to atone for his sins.
Kratos' height in comics varies depending on the artist's interpretation. But generally, he's depicted as quite imposing and towering over most characters.
Well, in this kind of fanfiction, Fenrir might be protective of Harry perhaps because he sees something special in Harry. Maybe he has his own reasons that are different from the normal perception of their relationship in the original works. It could be that Fenrir has a change of heart or there are some hidden plot elements that make him want to safeguard Harry.
In Norse mythology, Fenrir is a gigantic and terrifying wolf. He was born from the union of Loki and the giantess Angerboda. The gods were afraid of Fenrir's growing strength and decided to bind him. They made chains to hold him but Fenrir broke them easily. Eventually, they tricked him into being bound by Gleipnir, a special chain made with the help of dwarves. Fenrir is prophesied to play a major role in Ragnarok, the end of the world in Norse mythology.