Hush

From the Lego Batman Wiki

[edit] In The Comics

Hush, or Thomas Elliot was a childhood friend of Bruce Wayne's. He was also born into a wealthy family but unlike Wayne, he hated his parents. Driven by independence and wealth, he cut the brakes of his parents car which killed his father and mortally injured his mother. Dr. Thomas Wayne (Bruce's father) managed to save her though, something that really enraged Elliot. While at summer camp, he attacked a boy and ended up in a psych ward. He blamed his sudden outburst on Bruce and Martha Wayne. He would later be released by an intern named Jonathan Crane (later known as the Scarecrow). Thomas' mother later died of cancer leaving him with the whole family fortune. even though he went to Harvard and became a successful surgeon, he still held onto his irrational grudge against Bruce.
Later on, he would become the doctor for Edward Nashton a.k.a. Edward Nigma (also known as The Riddler). Nigma was diagnosed with terminal cancer and hijacked the Lazarus pit from Ra's al Ghul in order to cure his affliction. During this pseudo-mystical treatment, which renders the participant temporarily insane afterwards, the highly intelligent Nigma experienced an epiphany, "Bruce Wayne is the Batman". Afterward they discovered that they had a common hatred for Wayne, so Elliot and The Riddler decide to pool resources to bring him down. To this end, Elliot created the persona of Hush and set about his criminal exploits.

[edit] In Lego Batman: The Video Game

In Lego Batman: The Video Game, he can be unlocked after finding all 25 hostages in the villain and hero levels (Excluding the Vehicle Levels). He is armed with two revolvers.

On DS version he can be unlocked during the Villain Hunt and appears on the in game Batcomputer in the section labeled "Characters". His cost is 1,000,000 studs.