By enchanting a creature with Corrupted Conscience, you radically alter the math of the battlefield by granting that creature infect. When you then cast Shivan Meteor targeting that single creature, it deals a massive 13 damage, satisfying Imodane, the Pyrohammer's exact requirement of an instant or sorcery spell targeting only a single creature. Because Imodane translates that heavy damage directly to each opponent, the infect keyword from Corrupted Conscience steps in to convert those damage points straight into lethal poison counters, instantly ending the game for all of your opponents.