The "I am Vengeance" line is actually a reference to Batman's line from the comics but has recently been popularized by the marketing and release of The Batman (2022).
In the DC comics, Michael Amar, AKA Murmur, is an enemy of The Flash and a member of the Rogues. He was a doctor-turned-serial-killer, suffering from schizophrenia and going insane due to the voices in his head. Eventually, he went on a killing spree and involuntarily confessed his crimes. Murmur cut out his own tongue and sewed his mouth shut after his arrest to prevent incriminating himself again in the future. He also has a uniquely toxic blood type that makes him immune to euthanasia and allows synthesizing of a virus out of it.
There are two references to dictators in dystopian novels. The first is when they deem the rogues' unknown ally "Benefactor" who is the leader of the One State in "We" by Yevgeni Zamyatin. The second is when Iris calls Barry "Big Brother" in reference to "1984" by George Orwell.
The Red Death suit is similar to Savitar's armor, in that it hides the person inside completely and masks their voice. It's also multiple pieced in assembly and remote controlled as well whenever the user isn't present inside the suit.