Answer:
The only thing that can scratch Corundum is diamond.
Explanation:
We refer to the Mohs Hardness Scale for the hardness levels. We can see that Corundum is a level 9 which is the second highest so at a level 10 we see diamond, therefore diamond is the only thing that can scratch Corundum.
Some characteristics that is shared is a soft body and an outer shell to protect their body.