Spoilers ahead for Episode 19 of The Flash Season 4, called "Fury Rogue."
The Thinker has been several steps ahead of Team Flash for most of The Flash Season 4, and he scored a big win against them when he managed to kill Ralph Dibny, take out Edwin Gauss, and remove Killer Frost from the equation. The Thinker has worked his way through the bus metas, and Team Flash will have to get a very lucky break to gain some ground against him. The good news for the good guys is that the events of "Fury Road" presented a few big ways Barry and Co. may finally be able to defeat him.
Marlize Turns On Her Husband
The Thinker's greatest ally throughout Season 4 has been The Mechanic, a.k.a. his wife Marlize. A genius in her own right, Marlize helped transform DeVoe into The Thinker, and that alone should qualify her as one of the villains. As Season 4 has progressed, however, it has become evident that Marlize isn't quite as complicit as she first seemed. The Thinker has been using the Weeper's tears to control her, and she has figured him out more than once. The bad news is that he always manages to catch her and re-drug her before she can make a move against him.
In "Fury Rogue," The Thinker managed to alienate Marlize without necessarily letting her know that he's been drugging her. Despite her attempts to appeal to his feelings for her, even going so far as to put on what had been his favorite of her dresses, The Thinker dismissed feelings as unimportant, and Marlize was last seen weeping. If Marlize continues to wake up to how much of a monster he has become, she could turn on him, and her assistance could be the variable that enables Team Flash to get an edge on and defeat The Thinker.
Harry's Thinking Cap
The Thinking Cap developed by Harry enabled Team Flash to make some progress on fighting The Thinker, although most of the progress has been lost by this point, and he's currently deteriorating after he overloaded his Thinking Cap with dark matter. Harry is quite literally losing his mind, and he'll soon lose everything he ever learned unless he and Team Flash are able to find a way to undo the damage. Obviously this is a bad thing for Harry, but could it be a good thing for the fight against The Thinker?
The Thinker wears his Thinking Cap often on The Flash; if the good guys are somehow able to overload it with dark matter, it would enable them to incapacitate him without killing him. Barry and Co. were vehemently against the idea of killing The Thinker as recently as last week. Zapping his brain would allow them to stop him without ending his life. It would also arguably be morally worse than killing him since they would be depriving him of his ability to think for himself in any way, not just supervillainous ways. Sparing his life might make Team Flash feel better; zapping his brain could be much, much worse for him. If the priority is to be merciful as heroes, zapping his brain could be the worst thing they could possibly do.
Team Flash Kills The Thinker
Or maybe somebody on Team Flash could just go ahead and kill The Thinker. Ralph was all-in on the idea of killing him prior to his own death in the previous episode, and Team Flash hasn't shied away from taking the lives of their enemies in the past. I'm still not over the fact that Barry and Co. aged young Griffin Grey to death back in Season 2 when he was more confused than outright cruel, and killing The Thinker would almost certainly be for the greater good. Honestly, Team Flash should just considering calling Oliver over on Arrow to see if he could swing by to kill a guy for them. If Diggle can visit, why not Oliver?
In all seriousness, "Fury Rogue" saw Barry dealing with Ralph's death, and he revealed at the end of the episode that he learned more from Ralph than Ralph could have learned from him. Given that Ralph wanted to kill DeVoe, perhaps we'll discover that Barry realized that Ralph was right and he needs to permanently take The Thinker out as soon as possible. Would anybody really mourn The Thinker or be so outraged if Team Flash killed the bad guy?
Who knows? Maybe it will be a combination of these factors that Team Flash is able to ultimately defeat The Thinker. We'll have to wait and see. New episodes of The Flash air on Tuesdays at 8 p.m. ET on The CW. You can find out more about superheroes on the small screen on our breakdown of superhero TV dates. For some non-superhero fare, swing by our summer TV premiere guide and 2018 Netflix schedule.