Here is a list of other villains that can be done realistically, not saying they will ever, but easily can be done with todays technology
FireflyDetective Comics #184 (June 1952)Garfield Lynns, an orphan who became a pyromaniac and has developed a fireproof suit and flamethrower to further pursue his 'hobby'. He was originally known as a cunning criminal who invented numerous weapons that use light to commit crimes with.
Poison IvyBatman #181 (June 1966)Pamela Lillian Isley, a former student of advanced botanical biochemistry, employs plants of all varieties and their derivatives in her crimes. She has the ability to control/manipulate all plant life and is immune to all poisons and toxins. She is often described as fanatical about defending plants from other humans, even being willing to murder for her beliefs. She also has a severe love/hate relationship with Batman. In some instances she claims to love him, in other encounters she functions as an ally, and at other times she is more than willing to kill him.
Mirror ManDetective Comics #213 (November 1954)Floyd Ventris is a criminal scientist who uses mirrors in his crimes, in a fashion similar to Mirror Master. In both his meetings with Batman, Ventris tries to expose Batman's secret identity. Years later, Mirror Man returns briefly in the pages of H.E.R.O. #7–9.
SpellbinderDetective Comics #358 (December 1966)Delbert Billings (a.k.a. Keith Sherwood), is a painter who uses optical illusions and hypnotic weapons to commit crimes. Spellbinder is on the run from the law with his new girlfriend Fay Moffit when he is confronted by the demon-lord Neron, who makes an offer of immense power in exchange for his soul. Spellbinder declines, but Fay shoots Spellbinder in the head and accepts the offer for herself.Justice League International vol. 2. #65 (June 1994)A genuine mystic takes the name and appears as a member of the Government sanctioned "League-Busters".Detective Comics #691 (November 1995)During the Underworld Unleashed crossover, Delbert Billings turns down Neron's offer, and is shot by his girlfriend Fay Moffit, who then takes up the name Lady Spellbinder. (Detective Comics #691-692)