Guild Wars 2

i understand the hatred after the gods interfered in the war, but what made them hate each other before that?

Well… Looking at those scrolls in Orr, it would seem that after the gods put humanity on Tyria, Balthazar more or less declared them the master race and ordered genocide on the native races. Keep in mind, these are not creator deities, but rather interlopers from another world. They are likely something more like the Mursaat in that they are just long lived beings of incredible power, and not properly “God” (a kind of figure that the GW setting likely lacks entirely, unless you count the Alchemy).
While I honestly think Grenth and Abbadon are both kind of cool in their own ways, for the most part the gods are just terrible. They have shown themselves to highly prejudiced, senselessly destructive, and detached and irresponsible leaders. Upon picking this game up, I made a dedicated effort to learn as much of the lore as possible, and as I went on, I found in myself a growing hate for these so-called “gods”. My reading of them from the beginning of Guild Wars and onwards has left me wanting to kill them too.
Charr need no “gods”.
Tryia needs no “gods”.

Grenth, Abbadon, Melandru I respect. Even charr stories regarding the creation of Tyria credit Melandru.

Abbadon didn’t really do anything wrong before his imprisonment, he merely disagreed with the other 5. Grenth overthrew an unjust god of death, and for that, I will always support him.

-Drarnor Kunoram, the Eighth Reaper.

Very simple: In there powerlessness the Charr saw the huge power of the human gods. So they created there own gods. Or in other words: They found in the Titans there own personalization of gods. The Shamans/Shaman Caste led them in the name of (fiery) gods. Simultaneously the Shamans betrayed there people, because they knew, the titans were not true gods/the gods the Charr were looking for. The Shamans only searched for power; the power to controll, conquer and destroy. Pyre Fierceshot started a revolt, a couple of years after the searing (the day, the Charr invaded Ascalon) and free his enslaved people (especially sat the foundation for freeing the female Charr some years later) from the Shamans and there false gods. On that day he announced, that Charr does’nt have gods and dont need gods. And as you see: After the Charr broke the Shaman chains, they achieved true greatness. Reflecting on the slavery and the scam the Shamans did, and the progress the Charr did after they left the Shamans behind, it is not surprising, that they still refusing to obey some “gods”.

(<- From germany, so if you find bad grammar: keep it).

The Tyrian human Gods are much like the Greek gods, in that they are petty, back-stabbing deieties who only a fool of a human would rely on. But the main reason besides the Human gods basically setting their pet race on the charr and essentially ethnicly clensing their southern hunting grounds to build ascalon is that the charr had some pretty awful gods themselves. First it was the Titans, which were just monsters really, and ended up getting destroyed by the player, with advice from Glint in GW1. Then looking for a new god to keep their control on the warbands the flame legion shamans turned to destroyer worship. Essentially now they are as corrupted as the sons of svanir, just to Primordus instead of Jormag.
So to the majority of Charr Gods mean either meddling imortals trying to rearrange the world to suit themselves, or demons corrupt shamans sell their souls to in order to tyranise their fellow charr.

It’s also worth noting that a lot of Charr do not really see the Six Gods as true “gods”. Yes, they are incredibly powerful beings, but they can be fought and even killed, as Abaddon’s death showed. To the Charr, that means that the gods are not truly divine, omnipotent beings. A god who can be killed by mortal creatures is one that is unworthy of worship.