These would not be giant monsters but they would be big...and have a LOT of hit points.
Marvel has the Sentinels, Champions has the Minute Men.
They would be different, of course. They would detect and hunt down all meta-humans.
and they would talk.
The first encounter would sound like, "Unknown Meta-Human detected. Termination program initiated."
After you've defeated them, they would know you name. "Meta-Human, Black Falcon encountered. Termination program initiated"
They could be backed up by smaller 12' tall robots and a bunch of normal humans with big weapons but no armor (blasters and controllers).
They could fly and teleport into a city location. They would have a secret factory that assembles the robots (an adventure).
They could be an invasion force. Heroes and villains alike would be able to fight them. They could invade the PvP zones. They would even attack invading martians. and the heroes fighting them.
Termination program initiated.