Doctor Polaris aka Neal Emerson was raised by an abusive father but later revealed to be his aunt which drove him to become evil. He had a childhood interest in magnets which also drove him to create his suit which has magnetic powers. He was later killed but was resurrected as a Black Lantern.
SuccessorJohn Nichol later assumed the identity of Doctor Polaris but was later killed by the Black Lantern version of the original.
Justice League Unlimited
He first appears in the episode "I am Legion" where he helps Lex Luthor and The Key break into a top secret abandoned military facility. Although some Justice League members such as The Flash and Fire show up and try to stop them they all get away and go back to the Legion of Doom. He later appears in "The Great Brain Robbery" having serious doubts about Luthor's leadership to the point of wanting to over throw him. Regardless he aids the Legion in their plot but gets foiled but the League. At their headquarters they capture Luthor because it was Flash who switched bodies with him. When they switched back Polaris tried to kill Luthor but he overode his powers whether he is killed or not is unclear.
Batman: The Brave and the Bold
He first appears in the episode "Fall of the Blue Beetle" where he tries to rob a gold vault but Batman manages to stop him in time. He later appears in the episode "Aquaman's Outrageous Adventure" where he is seen lifting up a bunch of cars in a parking lot in attempt to steal them but was stopped by Green Lanturn.
Black Lightning Short
In the Black Lightning DC Nation short he makes a cameo at the end of the first one where he causing chaos in a town but Black Lightning went off to stop him.