Shingeki no Kyojin | Attack on Titan

All of these are explicit.

anonymous - "filled" on SNK Kink
Eren gets off on Annie beating him up in public. The writing is beautiful, and the author captures Annie's voice well.

Zee - "Black Me Out" on AO3
They didn't manage to rescue Eren from the female titan. Mikasa, sleep-deprived and furious at Levi, picks a brutal fight with him that involves (among other things) him choking her with her scarf. It turns into... something else. Excellent characterization for both of them (and Armin too), and the fight is well choreographed.

Vee - "Lay Down" on AO3
Extremely dark power dynamics: Levi is more or less Erwin's possession. Bondage, beating, orgasm denial.

J_deandra_j - "Dawk's Suicide List" on AO3
Noncon, Nile Dawk/Levi and Hitch/Levi. ( Description cut for possible triggers. ) Brutal and well-written; Levi's voice is perfect here.

Nonnamous - "Never Stray and Never Falter" on AO3
Reiner/Eren, with background Ymir/Historia; canon divergence for Chapters 42-50. Reiner and Bertholdt chop off Eren's limbs to keep him from trying to kill them. Before they've grown fully back, Reiner and Eren end up having (consensual) sex. Gorgeous writing, amazing characterization (especially for Eren, wow), searingly hot porn, a funny line here and there, and an ending that is both horrific and heartbreaking.