In a central collision of two 1 gram steel balls with a relative speed of 1 meter per second, nothing much would happen.
If the collision speed were much greater, say a few kilometres per second, they would, of course, evaporate.
Then, we also have the case where the relative speed is 99 percent of the speed of light. The collision is indistinguishable from an A bomb detonation. Entirely understandable and comprehensible.
However in the case where their relative velocity is almost the speed of light, where maybe an entire star or galaxy mass has been used for the acceleration, those two spheres will go through each other virtually intact!
Why do you think, this is?