Alexander Pushkin uses the characters in the story "Queen of Spades" to illustrate the theme of corruption. In particular, he uses the protagonist Hermann to show how corruption can lead to madness, but he also demonstrates the different aspects of corruption through some of the minor characters, whether they themselves are corrupt or whether they are negatively affected by Hermann's corruption. Puskin seems to be indicating that corruption doesn't just affect the one who engages with it willingly, but touches and affects all those who, even inadvertently, are in its path.
Hermann's actions seem to bring out the worst in everyone he touches, from the old countess to the innocnet Lisaveta. His desire to know the secret of the cards literally destroys the countess, emotionally destroys Lisaveta, and eventually, destroys Hermann himself.