John Doe wrote:

Is there a tool that puts tremendous force on metal, like to pinch the
end of a steel rod so that it flattens out a little?

If it's well-known, I guess all I need is the name.

I would like to put the steel rod through a hole and then pinch the end
of the rod so that it does not come out of the hole.

I picked up a bolt cutter thinking it might compress the steel rod as
it cuts. But it actually stretched the end of the steel rod so that the
diameter was less after the part broke off. I guess a powerful enough
bolt cutter with a dull attachment on the end?

Thank you.

This could be done in a few seconds with an oxyacetylene torch and a hammer.
Heat the end of the rod to red (won't take very long with a real O/A torch), put
steel block up to the back of the rod, WHACK the end is flat. Even easier if you
have an anvil or substitute.

GWE