Monica Padilla (Bayon after swap, original Bayon)
Following Episode 5: Monica's fate was sealed when she foolishly revealed to Kimmi her long-term plan to create a women's alliance against the men, which eventually would have targeted the men in her tribe. Setting aside her annoying comments to Kimmi about preserving the ocean ecology (which also seemed foolish when contemplating how hungry these castaways must be and how unlikely it was that they would remain on that beach for the remainder of the competition), it is Survivor 101 to not plot against one's alliance, no matter how far down the road, with another member of the alliance, since that member could easily have alternate plans which are more aligned with the current alliance. Monica's only reasonable option for sharing those plans would have been with Kelly Wiglesworth to plot first against Spencer and then later on (presumably post-merge) against the men. She was justifiably characterized as a snake at a phase of the game when the best plan is to hold strong with those whom you have shared the longest period of time on the island.