So, umm, the administration was actually using the weapon to keep the inhuman in check, right? It might not have been a smart idea to deprive them of their eyeball...

How about asking him to set a trap or something? Like, let's say, this guy makes the trap, then you or Maria go ahead and set it up. Wouldn't that technically count as him killing the monster?

Also, I'd like to recommend fire. Burn it to a crisp and eat it with ketchup afterwards. Maybe set a trap with oil and a lighter.

Acid is also a good option. Insecticide just couldn't do it tbh. Even drowning the thing in insecticide might not be enough. Droen it in acid and all you'd have would be acid.

I think the steam monster is like an amalgamation of ghosts. Like, many different people's minds combined or something. Just like the graveyard at the Goat Valley Campground, it could be all the people who got lost in the steam tunnels and couldn't find their way out.

Or all the people who opened the wrong doors in the steam tunnels...