Eteonicus was a Spartan commander during the Peloponesian and Corinthian Wars. He participated in many key engagements, held important commands and is mentioned multiple times by Thucydides, Xenophon & Diodorus. His appearance in the record however, is mostly episodic versus truly influential.
Read more about Eteonicus: Peloponnesian War, Encounter With The "Ten Thousand", Corinthian War