The woman was not fighting, not really, but she was struggling because she was very clearly terrified. That, along with the man trying to fight, made Barty want to up the ante. Moving his other arm around the woman, he severed her spine in one fluid motion, leaving her paralyzed. They knew magic, they could fix the damaged goods and then break them again, but the Muggles didn't know that.
Nodding toward the captured man, Barty said, "You're next. Let's go." The terror-stricken woman was limp in his arms, but he'd get her healed soon enough. The man was going to be the one who'd be more fun once they got to where they were going, anyway.