Don't know who he is? Well, maybe we should have said "familiar to a certain era of fans."
DuBois is one of three characters known as Bloodsport, and probably the most memorable of the three.
First appearing in 1987's Superman #4, the character was created by John Byrne and was one of the first new characters created to face the post-Crisis on Infinite Earths version of Superman.
Bloodsport uses high-tech weaponry, including sometimes Kryptonite bullets, and has the ability to teleport them into his hands from a remote location or tesseract.
DuBois was succeeded by Alex Trent, a white supremacist who appropriated the Bloodsport name while DuBois was in prison. Unlike DuBois, whose tech came to him later in life, Trent was experimented on as a child -- although he got the same powers.
Eventually the two would die, replaced by a third man -- or were they?
According to the DC Wiki there are three Bloodsports, but the third has only made a handful of appearances and has never been named. He took on DuBois's powers and looks like DuBois, so it is possible that he was either revived off-camera or that the writers and editors who used Bloodsport III were either confused or chose to ignore DuBois's death.
In his first appearance, Bloodsport (Robert DuBois) was a deranged man who snapped after seeing the injuries and trauma visited upon his brother during the Vietnam War.
After arriving on the scene ranting and teleporting guns into his hands so he could fire into crowds, Bloodsport revealed that he was going to prove difficult to catch becuase he had a rifle that fired Kryptonite darts.
This was right after John Byrne's The Man of Steel miniseries, so Kryptonite was borderline non-existent, making it clear to Superman and the readers that Bloodsport was working for Lex Luthor.
Not only did DuBois not realize that the mysterious benefactor who had outfitted him with his teleportation tech was Luthor, but he actually shot up one of LexCorp's properties at one point in the story.
Ultimately, Luthor was not prepared for the civilian casualties that would come with Bloodsport, having recruited him in the hopes that he could kill Superman by proxy and have deniability because DuBois was clearly in need of help. As Luthor security and Superman converge on DuBois, it is ultimately his multiple-amputee brother who talks him down, urging Robert to surrender to the police.
Because his story was one of misplaced anger and not genuine villainy, Bloodsport actually vanished at this point, going quietly to jail for several years in real time before making only his second-ever appearance in the comics (we'll get to it).
Just two months after Superman was "back for good" from his death at the hands of Doomsday, another Bloodsport appeared.
This one, too, had an agonizing and politically-tinged backstory but...a little less sympathetic.
Introduced when a group of thugs were beating up on a woman in an alley, it was at first implied he might be an antihero rather than an outright villain: he kills the thugs and "rescues" her.
That illusion is short-lived, though: Bloodsport also killed the woman he had just "saved," because she was black.
Bloodsport II came along at a dark time in the Superman titles. Following the death and return story, the titles seemed to embrace the grim and gritty nature of the early' 90s comics boom enthusiastically -- so much so that the week before Bloodsport's first appearance, Superman had failed to save Cat Grant's ten-year-old son Adam from being murdered. So pairing it with a murderous white supremacist was a bit on the controversial side.
The introduction of a new Bloodsport was also something that tied easily into the events of the titles at the time because white supremacist views and the ability to make weapons appear seemingly out of thin air made him an interesting foil for the newly-introduced Steel, a black man who had spent years developing military weapons and who had been horrified when some of those high-powered guns made their way into the hands of street gangs.
Later in that first appearance, Bloodsport took a group of hostages and tried to force Superman to choose between them by using two missiles; the Man of Steel outwitted the trick, of course, but it sets up a whole story of Bloodsport chasing after Ron Troupe, a then-recent addition to the Daily Planet newsroom who was also black.
In The Adventures of Superman #526, the two Bloodsports meet for the first time -- in prison.
In case you had not noticed from our illustrations, DuBois is a black man -- and so of course it is a bit awkward when he and Trent come to the realization that they share the same name and power set in spite of each one having an existential hatred of the other.
The violence was going to happen anyway, so the prison tried to mitigate the damage by having it be a boxing match which could happen within a set of rules and have guards there to keep things from escalating.
That is a self-evidently terrible idea, and the fight sets off a prison riot.
While Superman arrives to help out, he's managing the crowd while the main event takes place. Eventually DuBois gets the upper hand, but rather than killing Trent, he steals a Toastmaster (one of Steel's aforementioned super-guns), and tries to escape by blasting a hole in the prison gate. He is killed by prison guards, and Trent is brought back to his cell...but then burned to death by other members of the Aryan Brotherhood who were apparently dissatisfied by his performance in the fight.
As we said above, there is some question as to whether Bloodsport III is somehow DuBois or a new character altogether.
There is not much information about it, since he has not been used as a solo/stand-alone villain at all as far as we can tell.
Bloodsport III first appeared immediately following Infinite Crisis, when a mostly-depowered Superman was facing a new, Intergang-backed Superman Revenge Squad. Bloodsport was only one of a number of members, including Silver Banshee, Hellgrammite, Kryptonite Man, Livewire, Puzzler, Toyman, and Riot.
Many of those characters have been seen on Supergirl before, but what's arguably more interesting is how often Morgan Edge, a character who will appear as a major antagonist in Supergirl season 3, has appeared in the same stories as the Bloodsports (besides organizing this Revenge Squad, he also played a major role in a subplot in Alex Trent's first appearance).
The only other times Bloodsport has been seen is in a throwaway scene where Guardian stops him and Riot from trying to steal water during a disaster; and background appearances in the Salvation Run miniseries.