Eveline

Chapter: 8 · Finale · Guest House
Where: The Guest House attic and, after the cutscene, outside

Weak point

Her face and eyes; in the final phase, her open mouth

The final boss has three phases and two are scripted: you only need to deal enough damage between cutscenes. Before it, in the Guest House, the hallucinations of Mia with the chainsaw can't hurt you: don't waste bullets. The attic's NW corner has Shotgun Shells ×10 and Enhanced Handgun Ammo ×15 (only on this return). Arrive with grenade rounds and 44 MAG Ammo saved up: the mine Office gives you 2 Flame Rounds and 1 Neuro Round.

Reward

Credits and the ending you chose with the Serum: "End of the Night" (Mia) or "Just A Memory Now" (Zoe) achievement. The next run puts the Albert-01R in the Item Box; a Normal clear gives The Secrets of Defense.

About 6000 HP in her only non-scripted phase, probably the face (datamined). Melee does +320% and grows the further she advances; the 44 MAG does +25%. The Burner can't set her on fire. The structure is the same on every difficulty; on Madhouse, Grenade Launcher and 44 MAG to the face, and block every wave.

Step by step

Phase 1, walk up to her: she sends out shockwaves that push you back and hurt you, and you can't aim. Block (L) every wave (she telegraphs it loudly) and walk or run in between.
When you reach her, cutscene: Ethan injects her with the E-Necrotoxin.
Phase 2, the giant face: she turns into a huge face that crawls through the attic. Back up and shoot her face and eyes nonstop. If she reaches you before taking enough damage, or you get too close, she eats you.
Once she has taken enough she moans twice and grabs you with tentacles: move left or right so she can grab you. The fight only continues if she catches you.
Phase 3, outside: Ethan is on the ground and can only aim. When she lifts you by the leg, empty the Grenade Launcher and the 44 MAG into her face; then alternate handgun and shotgun, and only reload if you must.
A helicopter drops a crate with the Albert-01 and Chris tells you to take it. Wait for the tentacles to move away from her mouth and fire: a few direct hits end the game.