Silent Agreement

If the assassins succeeded in killing the mysterious girl that had invited Xavier to meet her, it was only a matter of time before the rest of the armed men managed to get in and sweep the penthouse. He'd eventually be found, interrogated and killed. Even if they didn't, the authorities would have to show up after such an event, which they wouldn't be able to keep under wraps if their boss died. His chances of surviving in that scenario were slightly higher, but everything he had built and his future would be ruined.

No matter how hard he thought about it, even if she had lost control of her organisation, she was still his key out of there. He needed her to get out of the building with his life. And past that, he needed to get his supplies to complete his mission, which he only had a day or 2 left to complete.