The object would have to contain infinite mass in order for a given force to not move it at all. If an object existed with infinite mass, the entire universe would implode instantly due to its infinite gravity.Renamedsin said:Blah blah blah unstoppable stuff and immovable object stuff.
If you magically stabalize the universe, and then fling another object at it that cannot be stopped (which would again be something with infinite energy) the two would collide and obliterate each other. The resulting release of energy would slowly disintegrate the whole universe.