How do you unlock the last two characters in Lego Batman?

Rescue all 25 hostages to unlock Hush.

Complete 100% of the game to unlock Ras Al Ghul.

Note: You must first spend 4 billion studs to unlock the last data item after buying all other data items.

Get true hero on each of the hero levels in story or free play.

The last two characters are self made characters made on the villain side of arkham asylum, you can make them look like anything you want and name them too.