Clayface

Clayface is a Villain that Appears in both Ben 10: Forces United and Ben 10: New Age and is a major foe of Batman

History
Ethan Bennett was one of the most respected members of the GCPD, and Bruce Wayne's best friend. Whereas his partner, Detective Ellen Yin, saw things in black and white, Ethan saw the gray in almost everything, and was more willing to allow Batman to co-exist with the GCPD. In fact, Ethan often found himself wondering if the caped vigilante he was pursuing was actually helping the city. During most of Season 1, Ethan defended Batman and his actions, while Yin often disagreed.

Clayface
In "The Rubberface of Comedy", Ethan's superior, GCPD Chief Angel Rojas, ordered the entire police force to take down every masked and costumed "freak" in Gotham City. Ethan protested, defending Batman as an asset to the city and credited him with helping to capture Joker. In response, an infuriated Rojas threatened to suspend Ethan, and told him to figure out where his loyalties lain. Ethan decided to prove that he's a good cop, and attempted to take down Batman, but during a scuffle with Joker, both Batman and Joker escaped. Later, when he investigated a break in at a museum, Ethan was captured by Joker, brought back to his hide-out, and subjected to psychological torture, which drove him to the brink of insanity. Yin and Batman rescued Ethan, but not before he was exposed to Joker's "Joker Putty" Formula; and inhaled it. Ethan began to immediately cough, and the formula took effect. (When the "Joker Putty" touched a surface, it turned it to just that: a malleable putty. Joker was about to spray Ethan with it, and said that he wanted to know what it did to humans, when Batman knocked it out of his hands with a Batarang, and caused Ethan, still tied to his chair, to inhale the fumes.) Batman captured Joker, who taunted Ethan as he was taken away. When Ethan told the media that Batman saved him and caught Joker, Rojas suspended him. At home, a depressed Ethan, still sick from the Joker Putty fumes, turned on the shower, and the hot mist in the room allowed the putty to take full effect, and Ethan's skin melted.

n "The Clayface of Tragedy", Ethan, horrified by his transformation, and unable to speak clearly (due to his throat full of clay) sought help in the city, but was attacked by the police, who used a fire hose to wash him down a drain. Ethan then kidnapped Rojas and attempted to kill him, but was foiled by Batman and Yin. Ethan demonstrated his ability to shape shift and mimic voices, and claimed that he could be anyone that he chose. Yin and Batman tried to reason with him, but Ethan claimed that Joker "didn't just melt my body, he melted my mind. I'm a freak inside and out!" After a fight with Batman, Clayface nearly killed him, but was stopped by Yin, who begged him not to cross the line and get blood on his hands. Clayface turned back into Ethan, and commented that he never thought he'd see Yin defend Batman, before he sadly asked: "Yin, what's become of us?" before he allowed himself to melt down a drain. During a talk between Bruce and Yin in a diner, Ethan appeared for a few seconds, and the two ran after him. However, Ethan disappeared before they could find him. They commented: "He could be anywhere. He could be anyone..."

In "Meltdown", Clayface went to Arkham Asylum to kill Joker, but Batman stopped him. Clayface later went on trial for his crimes, with Professor Hugo Strange giving him a clean bill of mental health. Ethan was put on probation: if he used his powers again, he would be put back in Arkham. Clayface became Ethan Bennett again, and got a job from his best friend, Bruce Wayne.

When Joker broke out of Arkham to wreak chaos, Ethan became determined to save others from his fate, and became Clayface again in an attempt to stop the Clown Prince of Crime. At first, he and Batman worked together to bring the crazed super-villain down, but after Batman confronted him for his violation of court orders, Ethan felt betrayed and nearly killed Batman until Joker convinced him to become a criminal. He became Clayface permanently and was put back at Arkham.

In "Grundy's Night", a Swamp Zombie known as Solomon Grundy, an old legend, attacked Gotham on Halloween. It soon turned out that he's really Clayface in disguise. Batman and Clayface fought in a wax museum where Batman defeated him and Clayface was sent back to Arkham.

Ben 10 Forces United
Clayface escaped prison back in Don't Laugh and went into hiding and finally decideds he wants to leave Gotham and start over by being the first to beat Superman in Clayface only to face Ben instead so he kidnapps Lois to lure out Superman where he is ultimately defeated by the duo.