You can get revenge on someone who has attacked you by using the Revenge option in your battle log.  To access the battle log, tap on the "envelope" button on your village screen.  Then, select the Defense Log tab and press Revenge.

There are a few things to keep in mind about revenge:
  • If the revenge button is not available, it means that player who revenge-attacked you, because you attacked them first.
  • You cannot revenge a player who has a shield or is online. If that's the case, try again later!
  • If you have a shield, you will be reminded that you will lose your shield by performing a revenge attack.
  • It is possible that you get no trophies for a revenge battle. Normally the matchmaking system would not match you up against that opponent, but the player still