So, judging by the order in which we face them, it looks like Extreme Ifrit might be the toughest.
However, having seen the videos with Extreme Titan, I shudder to imagine what they've done to complicate what is normally considered the most straightforward of the Primal battles.
However, having seen the videos with Extreme Titan, I shudder to imagine what they've done to complicate what is normally considered the most straightforward of the Primal battles.