Metallo (Lois & Clark)

In the second-season Lois & Clark episode "Metallo", Johnny Corben (played by Scott Valentine) was the boyfriend of Lucy Lane and, unknown to her, a petty criminal. Not only does he have a criminal past, but he's hitting on Lucy for money. Lois tries to convince her sister that Johnny's no good, but Lucy will hear none of it. Johnny was shot when a holdup went wrong and having fallen into the hands of Dr. Emmett Vale, a former Lexcorp scientist and his brother Rollie Vale, rebuilt into a Kryptonite-powered cyborg named Metallo and begins causing havoc in Metropolis. And, since Metallo is powered by Kryptonite, even Superman can't stop him. When Metallo kidnaps Clark to use him as bait for luring Superman, it's up to Lois and Jimmy to save Clark, but nothing can save Metallo after a final run-in with Superman, who, now aware of his Kryptonite power source, keeps his distance, using his super breath and heat vision to defeat him. Emmett is captured, but Rollie manages to escape with Metallo's Kryptonite, leaving Metallo dead.