I'm not sure specifically about 'lemon' fanfiction (which often implies adult - themed content). However, there are many great fanfictions about Kratos and Freya that focus on their relationship, their adventures together, or their individual character growths. You can check out popular fanfiction websites like Archive of Our Own and FanFiction.net, but make sure to abide by the site's rules and look for appropriate content.
Kratos might win. He has fought and defeated many powerful gods in his own world. He is not only physically strong but also very strategic. He could analyze the Hulk's movements and find his weaknesses. The Hulk, while strong, is more of a brute force fighter. Kratos could use his Blades of Chaos to keep the Hulk at a distance and then strike when the opportunity arises. Also, Kratos has faced opponents much larger than him before and has always found a way to win.
Tyrion Lannister. He is known for his wit and political acumen. Meeting Kratos, a powerful and straightforward warrior, would create an interesting dynamic. Tyrion might try to use Kratos for his own political games or just be fascinated by his stories of battles from another world.
Well, obviously Merlin and Arthur are the main characters. Merlin is the one whose secret as a Dragonlord is revealed, and Arthur is the one who discovers this secret.
One of the interesting Mimir stories in God of War 4 is about his past adventures. He was a very knowledgeable figure. He knew a great deal about the different realms and their secrets. His tales often provided valuable information to Kratos and Atreus during their journey.
In many 'Batman Beyond' fanfictions where Dana finds out, it could be about her finding out Bruce Wayne is Batman. Maybe she stumbles upon some evidence in the Batcave or notices some similarities in Terry's behavior to Bruce. For example, she might notice Terry's fighting style is similar to what she's heard about Batman's. It could also be that she discovers some secret technology related to Batman that leads her to the truth.
Maybe it's a mysterious figure from Merlin's past. Perhaps he had an encounter with a powerful magical being, and some kind of spell or pact led to the pregnancy. It could be a long - forgotten event that now resurfaces with this unexpected pregnancy.