Tempering

[Enkidoh]

Garuda seemed to prefer more to rely on brute strength rather than tempering though - she only resorted to it after the player beat her in combat, unlike Ifrit, who was more than happy to try tempering the player only moments after his summoning.

Considering Ifrit is fought at level 20 (and even his hard and extreme mode forms are considered tame), where as Garuda is fought at a much higher level, it's entirelly possible that Ifrit is simply overcompensating for his own innate weakness by tempering anyone and anything he can get his claws on, especially as a Primal's strength is connected, at least partially, to how many worshippers they have.

As for Titan, although it's not clear in ARR, in another thread I think it was either Moose or Noloe mentioned datamining had revealed dummied dialogue for the never-implemented Titan fight in 1.0, and apparently Titan actually indeed tempered some members of the Company of Heroes when they fought him, and simply killed those he didn't (this would explain why they're so hesitant about sending the player off to fight him directly in ARR - they saw just how dangerous he really was five years before.). In any event, it's obvious Titan too does in fact temper, but like Garuda seems to rely more on brute force than creating an army of zealous followers.

And then there's the wildcard - the dragonkin (the Dravanian Horde) and their currently unknown dragon Primal - Ishgard regards anyone suspected of having even minor contact with a Dravanian as a heretic, which on the surface simply appears to be typical religious dogma, however, visiting the cells at Whitebrim you can actually see suspected Dravanian supporters, and they clearly exhibit personality traits of tempered (lack of free will, zealous ramblings about how the dragons will destroy Ishgard etc), suggesting that the Dravanians too are tempering, and have in fact been doing it for years. But as to the identity of the Primal responsible is anyone's guess (it's clearly not Bahamut though, as he was contained within Dalamud for centuries after all).