race condition?: 2 class, 1 gameobject w/OnTriggerEnter, do all function calls execute in B if destroy gameobject in A?

HU$$anonymous$$$$anonymous$$, to be absolutly sure that is executed, put in OnDestroy() method a guard to check if this have been done, if dont call a function to do it.

also you can set custom execution order of scripts, and also, usually the objects are destroyed after the frame render (there exist DestroyInmediate() to zero delay clear...), but, if you want to be completelly sure, just check completion on OnDestroy method on script B, or last option, improve design, just destroy itself on script B if its colliding A after done the task and avoid the root of the problem