This will be the first decision you have to make in Foreclosed, should you kill the person who ordered you gassed. Ordered your implants to be taken out, which would be extremely painful. And he lied to his employer about you murdering Kyklos.
Whatever choice you make, nothing actually changes within the story. It's just a decision based on how you want to roleplay Kaplos. Do you as a player want to cause more damage over your run. Killing everyone who gets in your path because you're the victim in all this mess?
Or can you look above it all? That you're about justice and survival that no one needs to die needlessly, even though they wouldn't hesitate you kill you instantly. Can you take that moral high ground?
If you let The Expert live but just shoot to hurt him instead. Kapnos has a loud rant in the elevator that killing him would have made the world a better place, but no, you were after justice.—that's all that matters. Ignoring the multitude of people you have shot dead to get here in the first place.
If you shoot The Expert, Kapnos uses what The Expert said against him, that due to his ID being suspended, Kapnos doesn't exist. Therefore he didn't really murder anybody, from the law's point of view—nobody did.
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