User blog comment:LegerPrime/The Final Villian/@comment-26287497-20151013131420

It is a bit impossible for rogue to be the final villain but We can assume that Rouge is unstable. Remember the part when Natsu thought Gray will kill Frosch but Gray didn't instead he hug Frosch. Rogue was watching the whole thing and you would notice that his shadow became different a for a few seconds but it disappeared when Sting talk some sense to him. Maybe the Shadow (or maybe just maybe is ankhseram) is already giving him negative thoughts like saying frosch doesn't like him anymore. Also, he percieved the event as killing frosch's bond with him.