As a recap, most “Fighter of the Year” awards on other sites are really “Breakout Fighter of the Year” awards in that fighters who win, were usually not top fighters in the beginning of the year, but became so by the end of the year.
A fighter like this can and has won our FotY awards, but our award is more about maintaining a high standing during the award year by performing well a sufficient number of times and against a sufficient quality of opponents. It is more comparable to a season MVP in major team sports, not a playoffs/surprise MVP.
Winner: Amanda Nunes
Only two fights in the calendar year, but is now a double champion and cemented her place in the Top 3 All-Time (Women).
Runner-Up: Valentina Shevchenko
Like Nunes, she only fought twice in 2018, but also like Nunes, beat one of the best female fighters of all-time and picked up a championship in doing so.
3rd Place: Jessica Andrade
The third position isn’t as definitive as the top two, as you argue other fighters here, such as Ayaka Hamasaki. However, Andrade has probably established herself as the best non-champion on the female side of the sport.