“Is there such a mitigating factor under halacha that legitimizes the notion that some individuals are powerless to control their actions against an all-powerful YH?”
Halacha? No. (though we do find by anusa techila where at the end she was not anusa – the Gemara כתובות נא gives a reason יצר אלבשה” – but there has to be Anusa Techila.)
But there is such a concept Al Pi Kabalah/Chasidus; see sefer May HoShaloach of the Ishbitzer Rebbe R MY Leiner ZTL how he explains the story of Zimri in Parshas Pinchas (or Balak), and is quoted by his Talmid Rav Tzodek haCohen.