What supervillain appears in The Batman Adventures and from DC Comics?
DC Comics:  Most of their material takes place in the fictional DC Universe, which also features teams such as the Justice League, the Justice Society of America, the Suicide Squad, and the Teen Titans, and well-known villains such as the Joker, Lex Luthor, The Cheetah, Harley Quinn, Darkseid, Catwoman, Ra's al Ghul, Deathstroke, Reverse-Flash, Sinestro, Black Adam, and Brainiac. Harley Quinn:  She later appeared in DC Comics' Batman comic books, with the character's first comic book appearance in "The Batman Adventures" #12 (Sept. 1993).
Harley Quinn