Dysmey Post > Projects & Stuff > Bioshock 2 > Big Sisters
Sooner or later Little Sisters will grow up. Becoming more aggressive, more bestial, Dr. Alexander channeled their new-found hostility with mental and physical conditioning and a Protector-like suit of armor. After ten years time, they become the Big Sisters, an army of bizarre teenage human/machine hybrids, each of them something like a skinny Big Daddy in leather and leg braces, with remarkable plasmatic powers. They work to defend Rapture, and to ensure that nothing disrupts its way of life.
Running out of original Little Sisters, Dr. Sofia Lamb orders the Big Sisters to the shores of the Atlantic to kidnap little girls in order to turn them into Little Sisters.
The Big Sister is powerful: She slashes with her extraction blade. She slams into you. She throws things at you with her mind. She fires bolts of fire at you. When she is worn down, she drains the nearest splicer of Adam. She is a most formidable enemy.
But she is not invincible.
You can prepare for her attack: hacking security devices, making sure all reachable splicers are dead, stocking up on first-aid kits and Eve hypos. In fact, by her screech and the warning of a Little Sister (if you are carrying one), you can know in advance of her approach.
She is vulnerable to armor-piercing bullets and to electricity. Her oxygen tank is a perfect target. Basically, any vulnerability of a Big Daddy is a Big Sister's, too. She is distractible with Decoy. She can be fought by a Big Daddy befriended with Hypnotize. And, when she does find a splicer to drain, she is vulnerable during extraction.
Finally, when you do bring a Big Sister down, you get forty units of Adam, among other loot.