Simon

Simon's smile faltered around the edges. "You're supposed to be one mean son of a bitch."
"Van Cleef never said I was mean." He sounded very sure of that.
Simon's smile disappeared altogether. "No he didn't. He said you were dangerous."
"What would Van Cleef say about you?" Edward asked.
"Same thing," Simon said.
"I doubt that," Edward said.

(Obsidian Butterfly, page 487, paragraph 9)

* Simon recognizes Edward and calls him the Undertaker. He also used to work for Van Cleef, but he came in after Edward had already left.

* He is very observant, because he notice that Anita doesn't want to talk about her kills, but that Edward got her to talk about them.

* Before he died, Harold admitted to Anita and Edward about hearing Simon make a radio call to someone, saying that he had failed and that he needed someone to clean up the mess.

* Simon managed to shoot a wooden stake into Edward's back.

* Simon was eventually attacked by Quetzalcoatl, his lower torso ripped open and his intestines spilling out. He was still alive, and tried to crawl to his gun, but Anita kills him.