Self-tormentor is a challenging term to find synonyms for, as the meaning is quite specific. One alternative could be "self-punisher," indicating someone who inflicts suffering on themselves in some way. Another option might be "self-flagellator," a term traditionally used to describe those who physically whip or harm themselves as an act of penance. Alternatively, "self-inflictor" might work, indicating someone who intentionally causes harm or discomfort to themselves. Finally, "self-saboteur" or "self-destructive" could be appropriate, highlighting the idea of someone who undermines their own success or well-being.