Will Jones/The Comforter

In comics, Will Jones was traumatized when a man named Deacon Blackfire mobilized an army of homeless people that killed Jones' wife, beat him up and burning down his house. This lead to Jones making the homeless a target for his revenge. The comic book version of Jones discovered that he had the ability to phase people and objects and when he phased people, the effect was similar to that of microwaving them. Jones soon turned his abilities to killing homeless people with his powers, giving them the "comfort of death," hence his villain name, the Comforter

With Iris trying to keep the team running at STAR Labs and Wally picking up for Barry as The Flash, the Comforter might make a good minor villain for Team Flash to take on. A metahuman going around and killing the homeless would be something that journalist Iris would take interest in. They also might be someone that even Caitlin Snow — or Killer Frost — might even get involved in taking down.

Isaac Bowin/The Fiddler

While we know that the show has cast Kim Engelbrecht as The Thinker's sidekick, The Mechanic, we still think there could be room for one of The Thinker's comic book partners, The Fiddler. In comics, Isaac Bowin is a petty thief who learned how to use music to hypnotize and control others as The Fiddler. The Fiddler and The Thinker would eventually team up to remove all knowledge and memory of Keystone City from public consciousness. While that may not be The Thinker's master plan in the upcoming season of The Flash, bringing in The Fiddler might open the door for another musical episode. After all, executive producer Todd Helbing did tell Den of Geek that season 4 would have a lighter tone after the darkness of season 3.

Leonard Snart/Captain Cold

Okay, okay, we know that Leonard Snart is technically dead on The Flash, but we know that Wentworth Miller is reprising his role as Captain Cold on DC's Legends of Tomorrow. Maybe they can find a way for him to swing by Central City in some capacity? Last season's teases of Snart posthumously helping defeat Mirror Master and Savitar weren't enough. We'd like to see the anti-hero return for real, even if just for an episode.