How strong is the Hulk? Hulk survives the breath of Fin Fang Foom! (Hulk vs. Fin Fang Foom)
The Hulk is on an island where Nightmare is manipulating reality and turning Mindless Ones into other creatures, one of those being Fin Fang Foom.
Fin Fang Foom tries to convince the Hulk that he will rule the planet and that the Hulk should kneel before him. The Hulk isn’t playing that game so Foom breathes his fire on him and it barely singes the Jade Giant.
From: The Incredible Hulk v.2 #79 (2005)