Ok, so imagine in the spiderman universe, if some character like Dr Strange, started casting spells on people. Except NOT Dr Strange, because he wouldn't do this. But find a character who's able to cast spells and is a villain.
So this spell is just cast on a single random ordinary guy. He had no powers before the spell, but now after the spell he brings disease everywhere he goes. 50 mile radius around this guy. Everybody gets sick. While he himself never gets this illness. He's immune to it.
So whichever villain cast this on him did so and then framed the guy for some terrorist attack. So now this carrier of disease is sent to some max security prison. The idea being that the original villain is using this guy as a trojan horse to kill Kingpin, who's also locked up. Only problem is, due to some mix-up, the guy gets taken to a regular jail instead. All the inmates, and all the guards are dead within a month.
The other part of the spell is that if this guy is killed, the entire universe explodes. So you can't just kill him. But now NYC has this massive prison complex with thousands of cells, and only 1 prisoner. And they can't put any staff or inmates in there, or they'll die. They've been feeding him via remote control drone delivery. But that's a band-aid solution. So instead they build an artificial island off the coast. with a 75 mile restricted water access. On this artificial island they create ways he can grow his own food, and be self reliant.
Problem averted, right? Because now NYC can use it's already existing jail again. But now that the character is established, you can actually develop the character.
So remember, this guy was NOT a criminal. He did NOT have powers. He's just as much a victim in this, as anyone else. But the government treats him as a terrorist because of what happened at the jail. People see him as the cause of death, because nobody is quite sure whats going on. So they just blame him, and that's it.
After so many years on the island in isolation, he finds a way back to the mainland. And why? Because HE doesn't understand how it works either. He just wants to live a normal life, and doesn't understand why everyone around him keeps dying. So he comes to the city, in search of his family.
Then yada yada spiderman somehow finds out that if he reaches the shore, thousands will die. If he gets close to the guy, he'll die. And with that, we have spiderman using help from Tony Stark to use autonomous Ironman suits to essentially swoop him up, bring him back to the island, and then talk to him via video conference. And this is where we find out that he's not a bad guy. He's just frustrated, scared, and alone. Spiderman empathizes with that, and starts being this guys friend with daily chats.
And now, you have set up for the future, a new character that can be used as a weapon against their will to kill an entire city if taken hostage somehow. He's powerful, because you can't get near him to fight him. But also, he's just a guy with the spell swirling AROUND him. All of his thoughts and motivations are NOT death. But death does follow this guy everywhere he goes.
I think it would be best if this guy when we first meet him is timid and weak, and apologetic for everything in life, whether it's his fault or not. And by the end, he can become completely deranged as a result of isolation, but still not a bad person. A tragic story of a life. And then you can use him against his will in the future.
Maybe Green Goblin's glider can go fly to him, and kidnap him. Then he's essentially used as a bomb. God dammit. I want his Super Villain name to be "Bomberman", but that's already a video game. That would get confusing.
You know how comic books are. Eventually he'll be full on evil. Or maybe mind controlled by someone else. Or maybe he has mental health issues. I hate to say it that way, but that's how comic book villains are written. Evil super villain, and then his motivations behind being evil is because he has mental health issues.
Now I wish this were a thing.