As per me, mostly it seems like "boon conflict" someone is given a boon by God A for protection and God B wants to attack him for something else. classic case is the banasura story - he picks a fight with krishna but siva is boon-bound to defend him and a war allegedly happens between siva and krishna bexause of that.
What are the other reasons for which two or more gods fight with one another? Do the reasons indicate a definite pattern?