If you are 75% good, your counterpart will be 75% evil.
If you are 99% good, your counterpart will be 99% evil.
What do you do if you meet your evil counterpart?
If you are 75% good, your counterpart will be 75% evil.
If you are 99% good, your counterpart will be 99% evil.
What do you do if you meet your evil counterpart?
I picture a matter/anti-matter type of cataclysm.