Does anyone know the unique characteristic of Krypton?

Answer 1

Its a Nobel gas, discovered on May 30, 1898 by Sir William Ramsay and and Morris M. Travers.

Its colorless, odorless and tasteless.

It can form compounds with fluorine and very few other elements under extreme conditions.

Or

It's the birth place of superman (doubting this is what you are asking, seeing as you posted under science.)

Answer 2

Krypton has a higher gravity than earth, and a red sun.

Answer 3

It can be forged into Kryptonite which can be used to defeat Superman