BioShock 2 Remastered

The first available opportunity to earn this achievement is at the end of Ryan Amusements

You must complete a whole battle and kill a Big Sister without respawning at a Vita-Chamber part way through.

Make a save just before the battle, make sure that you select the anti-personnel ammo on each weapon so you can just switch guns.

Its better to strafe rather than walking backwards or forwards.

This can be earned on any difficulty.

Play on Easy and you can kill her with no problem at all, she basically stands in three places and never charges if you keeo using incinerate.
Strafe left and right to avoide her incinerate bolts too.