Source: Action Comics #595 (1987)
Type: ReplacementJohn Byrne didn't just revamp Superman villains to fit in his new continuity, he also tried to give Supes new legacy villains. Superman's Rogues Gallery could definitely use the help. The Silver Banshee didn't QUITE work out. She's still around, but isn't especially considered a "Superman villain". Maybe she was flawed from the start. The original concept gave her a magic voice/touch combo that can kill anyone, so long as she hasn't already killed them.
Yes, it's an odd weakness required to make her first story work. She kills Superman, but when he returns as a ghost, she can't then kill that ghost. Not because a ghost is technically already dead, but because she can't kill the same person twice. Good thing for the hero impersonating Superman's ghost, eh? Can you guess who it is? Think fast, because I'm about to tell you in the next paragraph.
If you guessed the Martian Manhunter, then you were right! Take a leftover Christmas cookie from the jar. He can change shape and walk through walls, so there you go. And don't worry, Superman got better. She only voiced him into a deep coma. Super tympanic membranes and all that.