Two Metal Gear Solid 4 questions?

Question

First one is how do you kill that screaming thing in Act 5. Dont laugh, ive only just turned 13. I know you have to use the syringe on yourself so that she wont use you as a puppet, but after that she still invincible, when i shoot her. and secondly, is it an achievement finishing the game on liquid easy (easiest thing).

Answer 1

You have to shoot the dolls that she's carrying, she carries two, but you only have to shoot the Psycho Mantis doll ( the doll wearing the gas mask). You'll have to shoot it about 5 times before she drops it, when she does, RUN, not walk, RUN over to the doll and pick it up before she does.

You'll have to use the doll to kill her, you aim it like any other gun and fire, yes I'm serious. Then shake the controller like crazy ( motion-sensing, that's why)

There isn't any specific achievement for beating the game on Liquid Easy, but you might've earned some other emblems during the game

Answer 2

Shoot the puppets off her arms, specifically the Pyscho Mantis puppet then pick up the puppet, equip it, and use it against her.  You'll get whatever achievements that you acquired over the course of the game, such as Eagle for head shots.