This spell can't be countered.
Counter target spell.
"Someday, someone will best me. But it won't be today, and it won't be you."
Illustrated by Scott M. Fischer · Darksteel · #23
There are no rulings for Last Word.
Surge (You may cast this spell for its surge cost if you or a teammate has cast another spell this turn.)
Counter target spell. Scry 2.
Counter target spell you don't control.
Overload (You may cast this spell for its overload cost. If you do, change "target" in its text to "each.")
Counter target spell. Scry 1. (Look at the top card of your library. You may put that card on the bottom.)
Cascade (When you cast this spell, exile cards from the top of your library until you exile a nonland card that costs less. You may cast it without paying its mana cost. Put the exiled cards on the bottom in a random order.)