Who is actually under the mask? Lets narrow down the most likely suspects

Who is Red X

1. Jason Todd. Let’s start with the most obvious. He shares similarities with Todd in that he’s good at what he does, he’s is hardened and he’s one of the few people that knows everything necessary to be a thorn in Grayson’s side. His discontent for Grayson is well documented. If Grayson is still Robin, Red X is probably not a new version Red Hood created for the Teen Titans cartoon. A light hearted version, without murder and resurrection, could definitely have been plausible, but if Grayson is still wearing the R, than there needs to be a better explanation regardless of Beast Boy name-dropping Todd, essentially breaking the 4th wall. It’s not Jason Todd
2. Grant Wilson. A Ravager-inspired Grant could definitely hold his own against Grayson, but loses impact without an immediate explanation to his origin. Grant, as the son of Slade, has reason enough to hate Grayson. Grant Wilson is better without the mystery. It’s not Grant Wilson
3. A Cadmus cloned Dick Grayson. This is simply not an option because Cadmus was never a part of the cartoon. Had they brought Cadmus in, than the Batman Beyond storyline that saw Amanda Waller create the clone as a failsafe to ensure there always be a Batman-esque hero to patrol, protect, and instill fear, and do so under her control, would’ve been a great way to call back Red X as the bizarro-Robin. It was definitely not a clone
4. James Gordon Jr. Speaking of definitely nots, here’s a character the show could’ve done a lot with, under creative freedom. One mention of this crazy young boy, and Red X could’ve easily been Jr. It was not James Gordon Jr
5. Nite-Wing. If explored in this universe, the sociopath with a twisted, inadequate self-education based on an obsession with the greatest hero of his generation, Robin, could’ve been twisted into an obsession with Robin leading to something akin to “Single White Female.” Already frequently referring to himself in the third person, this sociopath, who does believe himself to be a hero, could’ve been a prime suspect if he was introduced. However, not near as good as Grayson, they’d have to up his game substantially. We all know Red X was not meant to be Nite-Wing
6. Wing How. While we’re talking wings, Wing How was the young hero, who died saving the lives of his team. What if, the cartoon took that and flipped it on its head. Say, combining the storyline of X-Men’s Morph, circa the 90’s series, with a dash of Jason Todd’s bitterness towards Grayson and used a tormented How as Red X. How could’ve quickly grown to resent the world’s favorite sidekick given that he died heroically and seems to have been forgotten. The potential is incredible, but, it positively was not Wing How.
7. Deathwing. Another wing. This one is a brainwashed dollotron of Professor Pyg. The poor victim thinks he’s actually Grayson. We know he’s not. We also know he is not Red X.
8. Talon. He is the Earth-3 sidekick of Owlman. This is as easy to write as it sounds and, we’ll, it would make sense that Talon is virtually an equal to Grayson, he wouldn’t be a very exciting answer to the long-standing mystery. Talon is not Red X.
9. Mitch Grayson. Dick Grayson’s brother in everyone’s favorite Batman movie, Batman Forever, ol’ Mitch may not have mdied at all. What if he he survived and stalked Grayson for years and... hold on, this being a thing, makes Batman Forever a thing and , that shouldn’t be a thing. It better not have been Mitch Grayson
10. Fledermaus. This guy was the kid Nazi sidekick to an adult Nazi that went up against Sandman and Sandy the Golden Boy. Maybe Fledermaus was on a mission to make all sidekicks obsolete and we were witnessing slow, methodical psychological warfare. I’m betting we were not and Fledermaus was not Red X.
11. Saiko. A childhood friend of Grayson during his days in the circus, Saiko’s life changed after Grayson left to live with Bruce Wayne. After nearly drowning to death and forgotten, Saiko grew to become a deadly assassin and would turn his attention on Grayson. After learning of hi secret. If not for his mental instability, a far cry from the calm and collected Red X, I would suspect Saiko. Had the cartoon dedicated an episode to Saiko, he would’ve been a prime suspect, over Todd and Wilson, I suspect. Saiko however, is not Red X
12. Shrike. As a teenager, the boy known only as Boone was a friend of Grayson. As Grayson was learning under the tutelage of Batman, Boone learned from many teachers, to include Ra’s Al Ghul. He was soon part of the Vengeance Academy that Shrike operated in Gotham City, training young teens to become assassins. Grayson infiltrated the school after and formed a friendship with Boone. After Grayson’s interference led to Shrike’s death, Boone swore to avenge his master. Taking on his mentor's name, the new Shrike became one of the world's foremost assassins before returning to America to drive Robin mad before assassinating him. Shrike IS Red X

That being said, Shrike, and/or Red X, need to be a part of DC’s Titans tv show.