Plasmus is a villain from the Teen Titans TV series.
Origin in the comics
Otto von Furth was an east German miner who got caved in along with his fellow miners. In the mine were very dangerous radioactive chemicals. When he was rescued he was the only one left alive. He was later kidnapped by General Zahl and transformed into the giant hulking acid beast known as Plasmus. Plasmus regrets not being the one not to finally kill Zahl. he was later approched by the Brain to become a member of the Brotherhood of Evil. As a member he frequently fought the Teen Titans and enjoined the fights very much. During the Salvation Run story line he joined most of all the other supervillains as a prisoner on the alien planet. He was later used by Lex Luthor to power the device that they needed to escape the planet and was presumed dead after the device self destructed, however in the New 52 he returned alive as a member of the Brotherhood.
Plasmus started out as a young man with a condition that transforms him into a monster whenever he wakes up. When Cinderblock broke him out for Slade to use, Plasmus started to consume toxic waste. He proved to be a formidable foe without Cyborg on the team. After Cyborg re-joined the Titans, they were able to defeat Plasmus and make him fall asleep.
Plasmus later appeared in several other episodes. In one episode, Plasmus' appearance changed. He aquired green bubbles that, when popped, spat out acid. When Terra joined Slade, she broke out Plasmus, Overload, and Cinderblock. They were used to weaken the Teen Titans before Terra finish them off. They appeared once more and this time combined together and formed, Ternion, but were still defeated.