Eowyn vs. Aragorn

[Sir Kohran]

Frodo defeated Sauron

Hardly. The only people in Middle-Earth who can claim to have done that are Elendil and Gil-Galad (or Isildur, depending on the version). All Frodo did was do something that led to Sauron's defeat.

If it was Sauron in one corner of the ring (pun intended) and Frodo opposite him, somehow I would doubt whether Frodo could 'defeat' him