Chainsaw Majini (Shanty Town)

Chapter: 2-1 · Port and Shanty Town
Where: Shanty Town: he bursts through a door as you climb the stairs toward the exit gate. 5–6 Majini come with him and seem to respawn. At the foot of the eastern stairs there is a transformer on a pole and explosive boxes.

Weak point

The head (shotgun, machine gun, S75) and his hands as he raises the saw: he staggers and opens the melee combo. An explosion, a Flash Grenade or a leg shot makes him kneel.

Tall, lanky, with a bag over his head. One chainsaw hit decapitates you; caught by the tip only, you go into DYING. He is slower than a normal Majini: keep your distance, aim for the head and melee when he staggers.

Watch the Majini with him: if one grabs you, the chainsaw can finish you off. Kill whoever gets close first.

Reward

Guard's Key (needed to leave). Past the gate, a chest with gold and gems. Figurine: 10 BSAA Emblems and Chapter 2 cleared.

Attacks: swing type 1 (always screams or laughs first with a clear wind-up: step out of the arc; death or DYING by distance), swing type 2 (no scream, faster: death), 180° swing if you knife his back or stand behind him (death) and berserk after the fake death (slow wild swings while chasing you: DYING).

Berserk happens on Veteran and Professional, and on Normal if you haven't died (dynamic difficulty).
He comes in a red variant (less health) and a blue one (about twice the health, always gets back up). Both appear in the story, where they behave the same; the difference shows in The Mercenaries and Desperate Escape.

Step by step

Fall back to the transformer on the pole at the foot of the eastern stairs and the explosive boxes; lead him past them and shoot them.
Shoot his head or hands when he raises the saw. If he staggers: Hook / Twist Kick, then Straight / Roundhouse.
Explosion, blinding or a leg shot → he kneels → Uppercut / Somersault.
An Incendiary Grenade burns him and the crowd; Hand Grenades work too. You can also kick a door open into him.
If he falls slowly, saw in both hands, face up and with the chain still running, he will get up berserk: back off and use a rifle or machine gun. One grenade or Proximity Bomb stops the charge; a second kills him. He is truly dead when the saw goes silent.
Pick up the Guard's Key. You can grab it and run: there are no enemies past his door.