The markers that research has repeatedly found around the worst outcomes

Campbell JC, Webster D, Koziol-McLain J, and others (2003). Risk factors for femicide in abusive relationships: results from a multisite case control study. American Journal of Public Health, 93(7), 1089 to 1097

Comparing cases where a woman was killed with cases where she was not, the study identified a set of markers that recur: violence getting worse or more frequent, threats to kill, a weapon in the home, pressure on the neck, forced sex, violence during pregnancy, extreme jealousy and constant monitoring, threats of suicide by the partner, stalking, and a recent separation or a stated intention to leave. This is population level research, it cannot say what will happen to one person, and we have left the identifier off this line because we could not confirm it.