Deathmask; whisper it when you say it...
Even among the elite of Villain-Net, he is only a rumor. If a villain has failed too badly, or succeeded too well, they may receive a visit from him. They may have created impenetrable defenses and surrounded themselves with loyal guards, but they will still receive a visit from him. He will visit them, and their career will be over, permanently.
Deathmask is the ultimate enforcer for Villain-Net. He will eliminate any villain that fails to comply with Villain-Net's agenda, and then he will ruthlessly seek out and eliminate any and all loose ends. Friends and family, collaborators and acquainances, until nothing of the villain's plans can remain.
Few have seen him and lived. He has more powers and abilities than anyone should be able to accumulate, access to whatever equipment he might need, and almost supernatural levels of skills. Is he a demon? Some kind of strange alien? Maybe a construct of the Hell Forges themselves, purpose-built to serve Villain-Net's needs for an enforcer?
What happens to those he abducts in the process of removing loose ends? It certainly can't be anything nice, for they are never seen again.
When the villains of Villain-Net say his name, they whisper it, because to say it any louder is to invite his presence, and no one wants that.
And now, he's in your Hot Chicks campaign.