Shock Level 5 is a good candidate for Dan Dennett’s universal acid: an idea so corrosive that if we let it into our minds, everything we care about will be dissolved. You can’t change anything in the multiverse—every decision or consequence that you don’t make will be made infinitely many times elsewhere by near-identical copies of you. Every victory will be produced, as will every possible defeat.
I’m surprised this didn’t link to Bostrom’s Infinite Ethics [pdf].