Dangerous Weapon
Lethal Weapon
A villain vessel is a vessel used by a villain. This vessel holds bullets, and is a dangerous weapon.
きょうき
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
「アチョーーーーーー!」と叫び声を上げながら、コウイチはビエトの手から凶器を叩き落とした。
As he screamed, "Achooo!" Koichi knocked the dangerous weapon from Viet’s hand.