As we saw in §3.1 it is common to treat liability as a one-to-one relationship between a threatener and her victim (McMahan 2017: 5; Rodin 2011a: 99; Kamm 2011: 134–135). On this approach, we ask whether Attacker, rather than Victim, ought to suffer harm, and then, separately, whether Villain, rather than Victim, ought to suffer harm. This assumes that we can judge the necessity of harming Attacker independently of the necessity of harming Villain, and vice versa. But in Multiple Threats, Victim needs to harm only Attacker or Villain to save himself. Harming both violates the necessity constraint, but we can see this only by moving beyond the one-to-one relationship between Victim and each threatener. Moreover, it seems that necessity dictates which of the two should be harmed: Victim should disable Attacker, since this is less harmful than disabling Villain, and achieves the same end of saving Victim (Tomlin 2020; see also Draper 2016: 114–115). If, as McMahan argues, necessity is internal to liability, liability cannot be about these one-to-one relationships either. Rather, liability must involve comparisons across threateners.