Is there a rule for how high my character has to be for aggressive creatures are no longer aggressive to me. My best guess was that my character had to be 1.5 times the level of the aggressive creature for it not to attack me instantly.

You have to be about twice the monster's level for it to not attack you.

2x monster level+1 defines agressiveness.

there are a couple of exceptions thou

 

 

 

fleshcrawlers attack regardless of cb

 

there 35cb and they attack everyone (its y its such good xp)

Monsters in the wilderness are all agressive, and some monsters like Dark beasts are always agressive. Monsters usually get unagressive after ~15 minutes.

 

 

 

It is worth noting that if a monster attacks you first (and you don't attack it at the same time) you lose a attack turn. (I think...)