It is important to note that these "frontrunners" have only been not winning recently:
Matt (S7) [his KO was montaged though..]
Sawyer (S8) - winner
Jordan (S9) - winner
Alisan (S10) - winner
Billy/Ali? (S11)
Chris (S12) - winner
Chloe/Brooke? (S13) - winner, third place
Brynn/Britton (S14) - winner, second place
Kennedy (S15) [battle was montaged]
Maelyn (S16) - winner
Katie (S17)
Thunderstorm (S18)