In 7, part 1, the characters were darker. The horcruxe showed the audience their darkest of secrets and their fears and all of their inner turmoil.
In 8, part 2, the movie was darker. Just because we got to see a lot of Voldemort and what he is capable of. When we see him walking in the pools of blood with all the goblins lying dead on the floor, that was the first glimpse of how crazy and insane he is. Snape's death was dealt with in a scary manor. I thought it was brilliant. It added suspense and 심장 break. But in 8, we also see our characters greatest strengths.
Between the two parts, I'm leaning toward part 1. Not just because of seeing our characters in a different way and out of their comfort zone, but also because they are completely alone. And their frustrations with not know how to go about the mission. I think the helplessness aids to the darkness of the film. In part 2, they weren't alone. They had an army on their side. So, yeah. Part 1 I feel is the darkest film. Part 2 is right behind it though. Lol