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?
Get someone to do a very long set of interviews, thought experiments, and tests to see what makes us different in order to isolate, regardless of whether we can tell which of us holds the evil position, what areas of belief can have a position than can be objectively called evil. It’d be hilarious if, after months of testing, it turns out the only difference we have is our opinions on marmite or pineapple on pizza.
That’s a smart move. But won’t your evil self be interested in screwing the experiment uo?
Only if successfully completing experiments is itself good or evil. The question stipulates they are our moral inverse, not opposite in every way.