From Pluralpedia, the collaborative plurality dictionary
confronter (adj.)
CoinerJubilee System

A confronter is a alter similar to an exposure therapist, in that they expose themselves or others to trauma or triggering topics, whether to try and help them through it, curiosity about how they or others will react, or for fun. This is not always a bad thing, and these alters usually have the best in mind for their system.

A simple definition is "an alter who 'confronts alters with triggers and trauma.