Solomon Grundy

Over a century ago, murderer Cyrus Gold sought to escape justice by hiding in Slaughter Swamp, where met a fate worse than death. Mysterious forces doomed the now immortal Solomon Grundy to an endless cycle of death and rebirth.

Zombified
Mass Murderer Cyrus Gold sought to escape justice in late 19th century Gotham by hiding out in Slaughter Swamp. There he met a fate worse than death: captured by Ra's al Ghul and his League of Assassins, Grundy was repeatedly killed, revived in a Lazarus Pit, and experimented on to see what effects prolonged use of the Lazarus Pit would have on Ra's.

In the process not only was Cyrus permanently transformed into an undead swamp monster, but he was also robbed of his memories as Cyrus Gold. Soon Cyrus became too powerful to control and escaped the League only to be captured by a circus and worked in a side show, thusly rechrisened Solomon Grundy after the famous nursery rhyme. After the circus went under, Grundy was buried where Penguin's famous Iceberge Lounge would be built. Solomon Grundy was found in the Iceberg Lounge by the Penguin when he took over Cyrus Pinkney's Institute of Natural History in Arkham City. Penguin frequently fed disloyal subjects to Grundy; when an undercover Batman questioned Penguin about the identity of "the man downstairs," Penguin simply told him to pray never to find out. Later, he fought Bane (when he came to claim Penguin's titan) and won.

Batman: Arkham City
After Batman has disabled the Freeze gun Penguin was shooting, he knocks him off his vantage point. Before he can finish him off, the Penguin detonates the ice sculpture that Batman is standing on, and he falls into a pit. Penguin then unleashes Grundy by electrocuting him.

Batman uses the sources of the electricity to his advantage by using Explosive Gel to destroy the sources, causing Grundy to grow weak. Batman uses a beatdown to finish Grundy off, but Penguin enables the sources of the electricity to turn back on. This time, the sources are only open for a small period of time, making it harder for Batman to place the Explosive Gel on them. After destroying the generators for a second time, Grundy appears defeated. But before Batman can completely defeat Grundy, he grabs Batman, and crawls over to the main generator. He then sticks his arm into it and gets regenerated yet again.

Batman is able to escape Grundy's grasp, and, with much difficulty, finally defeats Grundy by completely shutting off all power and then punching his heart out after destroying his rib cage with repeated blows to the chest. Grundy is now defeated and Penguin has no backup, but himself and a grenade launcher.