As part of an edited Brill volume, Korinna Zamfir has produced an essay on the opponents in 2 Timothy:
Korinna Zamfir. “‘Beware of Him, for He Strongly Opposed Our Message’: Antagonisms and Identity Construction in 2 Timothy.” Pages 162–73 in Antagonismen in neutestamentlichen Schriften Studien zur Neuformulierung der ‘Gegnerfrage’ jenseits des Historismus.” Edited by Stefan Alkier. Beyond Historicism – New Testament Studies Today 1. Leiden: Brill, 2021.