Obviously Ignia should be the overall winner here, question is who the remaining three would be in this battle royale.
Id guess Ignia would start with a huge aoe fire blast. Now question is would he go for a seemingly no-effort casual one like he did against Natsu and Suzaku, or would he go all out. The casual one is survivable since Suzaku managed to survive it (in Natsu's case he resistant to fire), but we saw that Suzaku can take a beating or at least block a lot of punishment like he did against Selene and Natsu. A serious al out fire blast on the other hand, im really not sure how many here are surviving this.
Scenario with a casual Ignia fire blast, Suzaku is able to survive this with some damage, Irene is surviving this by enchanting the fire or whatever the hell her bs magic does, Gildarts i would argue is the sturdiest of the pure human characters here so he is definitely tanking that with little damage done, Gajeel should be able to tank it with iron body but with some damage, Skullion is fucked lol since he is ash, Kiria would probably barely survive this, as for Brandish people made the solid argument where she could go giant where Ignia (in dragon form) is almost as big as her pinky toe if not smaller, so i guess she could avoid a lot of damage done to her but still gets damaged.
So Kiria and Skullion are out of the game from the get go. Skullion gets royally fucked since he is ash and Kiria should get fairly damaged, enough for someone to capitalize on it (by every other character that survived it). Once Ignia saw how many survived he would probably take it up a notch and go wild either with a really serious aoe fire blast or go for a specific individual. Personality wise i can see him go for the strongest here which would be Irene. I could also see Irene playing a smart game and distance herself with flight either in human or dragon form. This should give her some upper hand since i dont believe Ignia in human form can fly, or at least i havent seen him fly. Meanwhile i can see an all out brawl between Gildarts, Suzaku and Gajeel, while Brandish goes for organ bursting or for another round in giant form where she could literally stomp or kick them away as far as possible, but that would be a bit dumb since her giant form would be a huge target for Irene and a serious Ignia. Irene would probably undo her magic and nuke her or Ignia would incinerate her with a full out serious blast. So smarter move is stay small and go for organ burst.
Im not seeing Gajeel surviving the threesome nor do i see him survive Brandish's magic. I also think Brandish's magic could down Suzaku as well, but only if he gets distracted by the threesome. If for example Brandish goes for anyone besides Suzaku i think he would notice her immediately and go for his super speed killing slashes which i dont see Brandish surviving. So i think it really depends on whom Brandish targets first. Then again Gildarts can use Brandish's distraction to just crumble the remaining guy. Also Suzaku's sword should be useless against Gildarts since his magic would just crumble it into pieces.
Hm, i see im once again playing and bit of favoritism and trashing on Diabolos like always but lets go with:
Ignia, Irene, Gildarts and Brandish lol
A lot of my thoughts here are shaky but fuck it