Actually, no. You were not required to kill Anna. You could stay idly by and let her shoot Lebedev.FaceFaceFace said:The original required you kill one character to proceed (Anna Navare), but gameplay-wise you didn't have to do so through combat. He didn't really say whether or not these required bosses have to be fought directly with guns or if there are other ways of killing them, which I guess would determine how much of a misstep it is.
The one person you really had to kill is Walton Simons.