There's two points to note about this comic.
As the comic opens, Iron Man is on his knees in damaged armor while Ultimo stalks towards the White House. The book is massively overwritten by Bill Mantlo as was the style of the time.
Iron Man lures Ultimo into following him. Given a few minutes to recover in a jet that happens to be piloted by a former ally, Iron Man bails out to return to the attack. He smashes Ultimo in front of the Lincoln Memorial - this should have knocked the android into the reflecting pool.
And then as they continue to battle comes the second point we should note. Iron Man begins digging a tunnel and luring Ultimo down into it.... as an alternative to "mobiliz[ing] a tactical nuclear strike..." Calling in a nuclear strike on DC, on the grounds of the Lincoln Memorial and roughly two miles from the White House and right across the river from the Pentagon doesn't seem like a very well thought-out plan.
Fortunately Iron Man is able to dig deeply enough to engulf Ultimo in magma, somehow avoiding setting off a volcano in Washington, and the Ultimo story ends. Until the next time he shows up. And no, I don't know why an android needs a loin cloth.