1. There are dozens of supervillains (outside of prison) who are old and presumably want to not die of old age! (It would be higher, but supervillain is not a very low-risk profession.) Almost half of them are in the Caribbean island of Novapest, ruled by the Titanium Tyrant, and he tops the list of people who would want to take over the world, as he tops most supervillain lists; the world's most infamous villain, inventor of non-tinker powered armor, ruler of his own kingdom, and one of the overall scariest people on the planet. No powers except being implausibly intelligent and ruling his own country, but his wife has mind-control abilities, his older daughter is some kind of juggernaut, his son can control any electronic devices, and his lieutenants include a power copier with multiple A-ranked combat abilities, a 400-year-old alchemist, Steelstorm of Steelstorm Industries (the world's leading manufacturer of tinker weapons and killer robots), and Legate Livia. His attempts to get a reliable source of immortality for him and his friends were recently interrupted by a major rebellion, which he is currently putting down, and Novapest keeps coming in and out of contact with the rest of the world as his impenetrable-force-shield over the island rises and falls, but it's pretty clear that he's going to win eventually.
Probably he would just be willing to give her money, but observably Livia wasn't.
Other possibilities are... ambiguous. The term "Nine Nightmares" was coined by the New York Times to describe supervillains or supervillain groups at a tier of power above ordinary supervillains - the villains who can treat ordinary superheroes the way ordinary supervillains treat regular people - and those are the obvious place for an attack to come from, but there are a lot of villains out there, villains as mentioned keep dying, and everyone has their own list of who's scariest. Right now the general-consensus list of the Nine is Voidwrath (A-ranked "living alien invasion", not the kind of thing that ages), the Tyrant and his Royal Court, Feast (A-ranked cannibalistic power-thief, already immortal), Magister Magistrorum (A-ranked "tinker demonologist," already immortal in the 'eight or nine hundred years old' sense), the Empyrean Sage (A-ranked "space tinker" with armies of weird robots), the False Sage (you're acquainted), and then all the lists diverge because everyone else who unambiguously deserves a spot on this list is already dead. Possibilities include:
- Hecatonchire (B-ranked mysterious force that possesses people and turns them into monsters, US-based but nobody knows more)
- Ithalimor and the Synthetic Angels (a collection of high-B-ranked tinker-made constructs with ridiculous powers who tried to destroy human civilization like ten years ago; supposedly they're mostly dead or reformed or in jail but they were really scary in a fight, Ithalimor is very clear from her cell that she intends to wipe out all human life just as soon as she gets out)
- Mechanos (A-ranked tinker roboticist, known as "the Scavenger Tinker" for his ability to use others' equipment, claims he's trying to prevent an inevitable apocalypse that superpowers will cause, pals with the Tyrant)
- Legate Livia (B-ranked idealist who can give 'perfection' with a touch and disintegrate anything she's perfected, is getting onto a hundred, looks like she's seventy; she was on the first list but, as her minions' fight with Musoka demonstrated, cannot really cut it at the top level any more)
- The White Lotus Prince (B-ranked probably-tinker possibly-idealist sorcerer, hasn't done anything supervillainous since he took over North Korea Joseon, claims to be immortal, who knows)
- And rather a lot more, since there probably aren't nine villains out there who can swat regular superhero teams like flies, and this means that every B-ranked or higher villain is prepared to plausibly argue for the ninth space on the list, even if they have no possible chance against the Atlantic Six.
If she's willing to track down older villains, there might be even more who'd be interested - Doc Fenris was major in the 50s and 60s, retired to Alaska in the 70s, and hasn't been seen since, and there's still mob superstitions based on an unknown woman who took over the Five Families in the early 40s, ruled them behind the scenes for twenty years, and disappeared the first time the Atlantic Six noticed her - but there's a lot of history and it's had a lot of villains.
And, of course, there might be national governments. Dictators across the world age; the president of the People's Republic of China is seventy, the president of Russia is a nonentity and the head of the Russian Union of Superheroes is in his 40s but has friends who are older... Most of these would just be willing to pay her money, though.
The most serious threats are likely to be from the Tyrant and various of his people who also want to be immortal, with Mechanos and the Empyrean Sage topping the list of independents, but there's a *lot* of others she can read about. Most of them, however, are either much weaker than Blue Lantern or cannot actually survive in the thermosphere, and if you can just leave the planet at will that takes out basically everyone who might be interested in you outside the Nine Nightmares, Ithalimor's group, national governments and Mechanos. Possibly Magister would want to kill her just to be a dick; apparently he does things like that quite a lot, or Feast because he thinks he'll get Blue Lantern superpowers if he eats her heart. All the people who just want to be immortal would probably be willing to just buy immortality, though it's quite possible that the Empyrean Sage would be insufficiently sensible to qualify, since he basically does not talk to people except to deliver prewritten monologues.
More information is, of course, available if she wants it, and Minerva is happy to provide links to detailed analyses of her enemies' powers that she's already written about.