Big Sister 1/3 in The Surge is one of the easier bosses, and the special weapon drop is an incredible staff that has fire damage. I tailored my loadout for this fight to have lots of stamina and 12 total health packs. After the boss fight, note that there are NO enemies between you and the next med bay. If you run into an enemy, you have taken a wrong turn somewhere.
https://gaming.youtube.com/watch?v=IwfmKwiJtjI&feature=share