Yeah it was a great choice by the editors to put that one first, very good stuff.

It's "Words In An Unfinished Poem" by A.C. Wise, though I don't believe it's been published independently of the Sword and Sonnet collection.

Here's an excerpt:

“I hear you can kill a man with a single word,” Emmett says.

There’s a click in Emmett’s throat, a sound of fear. He licks his lips, glancing to the bottle at the gunslinger’s elbow. The gunslinger nudges it forward. Unasked, the bartender materializes with a glass then silently returns to the bar.

“Not only men,” the gunslinger says. Emmett flinches, spilling whiskey as the mouth of the bottle skips across the rim of the glass. “And not just a word.” The gunslinger reaches into their pocket. Emmett’s chair jumps back until he sees the movement hasn’t resulted in a drawn gun. The gunslinger sets a single bullet casing in the center of the table.

All the hair on Emmett’s arms, the back of his neck, and even his thighs, stands on end. There’s a word etched onto the casing, the lettering scarce thicker than a spider’s web. Before he can read the word, the gunslinger covers the shell with their hand, disappears it into their pocket, and smiles. It is the most unsettling expression Emmett has ever seen.

“I’m writing a poem,” the gunslinger says. An explanation that sounds like a warning, a confession, and tastes of sorrow. To Emmett, it means nothing.