Candyman was a fictional drug-dealer from Cloak & Dagger, a series published by Marvel comics - he is not a supervillain but does have enough knowledge of drugs to be a danger to the public and is also a very ruthless individual (as seen below).
Pillsbury, a severe drug addict, went to the police, probably because Candyman refused to deal the addict drugs without payment.
Atop an inner city building, desperate for another fix of smack, Pillsbury returned to Candyman. Unbeknownst to both of them, they were being watched by Cloak and Dagger. Feigning forgiveness, Candyman prepared a dose of 100% pure smack, enough to kill 10 men, even though the addict had the cash to pay for the fix. Candyman wanted to punish Pillsbury by giving him an overdose. After Pillsbury had injected the lethal dose into his own veins, Candyman revealed his murderous plan, and he slammed the addict against a wall, before turning to walk away. However, his exit was barred by the sudden arrival before him of Cloak and Dagger. Desperate to escape, Candyman took out his knife and swiped at Dagger, who deftly leapt over the dealer to tend to Pillsbury. Candyman then stabbed at Cloak, but was instead drawn into his cloak. Meanwhile, Dagger healed Pillsbury with her light, ridding him of his addiction. Cloak then released Candyman, who tumbled out, sweating and drooling, talking in shock of Cloak's internal cold darkness. Cloak and Dagger then teleported away, leaving Candyman lying on the rooftop.