Returning yet again to our analysis of the January I-HoD villains poll, the end of this long road of examining prospects and initiates into the The Vile Menagerie is finally coming into view. At eight votes each, these characters were recommended by 25% of all respondents, and as a group represent a "sixth place" showing amongst Martian Manhunter's adversaries. They're also amongst the top 25 foes of the Alien Atlas, based on your level of interest, signifying a real narrowing of the field.
A reoccurring Apokolipsian construct, Brimstone is visually strong, but the Evangelizing Godzilla shtick is only slightly easier to work into a Modern Age comic than Titano, the King Kong with kryptonite vision. Also, somehow, at least one Brimstone would seem to have sold its mechanical "soul" to the devil Neron. Being a child of the '80s, this isn't the first time I've seen an attention (and otherwise) whoring Bible thumper led into sin, but this specific example is kind of insane. Worst of all, it occurred at the height of Martian Manhunter's "fire weakness only psychosomatic" period. Brimstone's powers are more heat than flame based, so J'Onn straight up ripped Brimstone's heart right out of its belly in a matter of panels. I think that happened with the Jimmys after they lost their tithed luxury cars.
The former Mr. Bones was annoying in the '80s, when he was an Infinity Inc. anti-hero who spoke in rhyme and dressed as the Black Terror. At that point, Bones' sole relevance was as a prototype for Todd McFarlane's Spawn. In the late '90s, D. Curtis Johnson revitalized Bones as a seemingly sinister but ultimately altruistic regional director of the Department of Extranormal Operations, who spoke in verse so subtle you could miss it. The 1998 series certainly did, forsaking a nuanced portrayal in favor of making Bones another liberal conspirist evil government dirtbag who tried to extort information out of Martian Manhunter, and failing that, released most of his secret identities around the world to the public. Bones continues to be a presence in the DCU, including in that other Manhunter series, and filled a sort of reverse Mr.V role for a time.
The 1998 series tried to hit the ground running with regards to building a rogues gallery in the Martian Manhunter ongoing series. Like Miller & Certa before them, they instead offered a string of one issue wonders with potential they never bothered to explore through return appearances. The Headmaster/Headman could have been a contender, but all the love went to the deeply flawed Malefic instead.
American Secrets is a book I had to digest, because it's too good and complex to be appreciated immediately upon completion. Not only is it probably the finest Martian Manhunter story ever told, but also an unappreciated masterwork lost on the Vertigo groupies and poly-bagging speculators of the period. All that having been said, I don't really see the point of ever going back to the Master Gardener of Mars or his Lizard-Men. The latter is another of the countless variations on shapeshifting alien invaders in comics, and the former another misguided Martian survivor doing more harm than good. Dipping into that well would be like following Chinatown with The Two Jakes.
I experienced burnout after last year's The March of Mongul, but having rested up, I'm back to thinking fondly of the cad. He may be another variation of Jim Starlin's Fourth World fixation, but who better to fight a poor man's Darkseid than our own off-brand Superman? Everything the '98 series did with Darkseid that got under my skin would have been forgiven and even appreciated had Mongul been substituted. Superman has a notably poor rogues gallery though, and prior to his actually fighting Darkseid on a regular basis, Mongul served as one of his house villains for DC Comics Presents. So Superman got "For the Man Who Has Everything," which in this context takes on a whole other meaning, like "...and the Manhunter gets Nothing but Coal and Switches."
Professor Arnold Hugo
My adoration for Hugo is no secret hereabouts, so I'm not sure what I can add beyond a link and a prayer we'll see more of him someday. The prayer includes a requirement that Prof. Hugo retain his essence as mean-spirited but mostly harmless foil, because if you're just going to get nasty with him, what's the point? Dr. Trap has already filled the role of Hugo for the violence obsessed modern reader, and without ruining the inherent delightful silliness of having a gadgeted-up Peter Pumpkinhead as a primary opponent.