Wiktionary
placater
n. One who placates.
Usage examples of "placater".
A flood of self-help books describe ACA's variously as overly anxious and responsible, passive placaters, martyrs, apathetic, substance abusers, poor problem solvers, distrustful, out of touch with their feelings, unable to maintain relationships, codependent, shame-filled, suicidal, and so on.