[The Artist Formerly Known as Hawk]

It should be pretty obvious what Ifrits weaknesses are, seeing as his strengths lie in, well, strength and projectile attacks, his speed, reflexes and tactical abilty is suficiantly reduced. One analogy I always had in mind was that Ifrit is an endurance runner, as apposed to a sprinter, he can keep going for a long time, but he can't react well to quick strikes and can be out-maneouvered by speedier opponents. And he does kind've blunder into things without thinking, so unconventional attacks take him off guard.

Of course water is also not his friend; his firey mane, despite being inherently ignited by magic only keeps burning if there's still oxygen around, so dump him under water or in a vacuum and it goes out, and he can't create more in such an environment. Fighting in the rain would also be problematic for him as it would quench his main source of fire and force him to create more consciously for every attack.