Here a my video with fighting Gunnr with lv gear 4 , no fury, no resurrection at level: Give Me God of War
With low gear at this difficult one shot can kill you, so if you see, i will take first damage to see how much damage a non cirtical strike can give you, after that no more damage because is essential don't loose the combat flow and don't take more damage.
This is the first Valk but if you fight at this level of difficulty just after Modi and Magni, will be a challenge.
This valk have 1 attack wtih schyte that can be stopped by shield but you will make to loose your stability and make you vulnarable to next attack!
Second attack with schyte from the sky must be countered at any cost to make more damage and to avoid die, you can dodge but is very dangerous.
Third attack come with his wings, you can use shield for first and second hit, but at third hit you have to counter if use normal attack and dodge at your right side to avoid the red punch
Use Atreus shock arrow contiuosly, pay attention to not use runic power if you are not totally sure of a counter attack by the Valk or you will die miserably.