The white knights in the comments defending this shit tier writing (aria and licht) are hilarious
Coming from the same hate bandwagons in Maou no Musume, I'm saying this again - Japan may have a point when saying piracy affects their sale.
The story was laid clear from the beginning. MC got betrayed by humanity, swore revenge, found a group of insanely strong demons, got recruited by them, and aided them in their conquest against other 3 demon lords. Humanity played little in the story, and they have always been in combat against the demon (Rose's castle invasion, Mizuki's home under siege for failing to side with humanity, Faris' sister forced to slave for humans). After all that, we're witnessing human's final attack with a strong ally in the name of Tenebres - she needed a strong motivation against demons, and she had. If this was any other isekai story, she'd be the MC, win the game and lived happily ever after. Instead, this is Licht's story, and naturally he prevailed.
Just like with Maou no Musume, I'm seeing a concerning trend here - readers of a "particular" story narrative coming across a series that goes against their expectation, and rather than dropping it, they stuck around and throw criticism that made no sense (given the series' setting). This series reached its ending after 10 volumes, it was popular enough to stay relevant till the end because JP readers actually voted. The global audiences simply consumed free scanlations and complain like they're entitled to the product.