He could shatter glass but he couldn't pull a gun on him to kill him?? Or just jump on him and bite the shit out of his neck, zombie style with all the flesh and blood??? Like what even is the good use of your Vampire side if you don't use it. We already know Wren can survive on Tristans blood, so there is no use from keeping the old creep alive
Guys don't shit on Alpha, he has trauma from bonding. His parent was bonded omega and he saw first hand what that does to them when they are abandoned. In his twisted logic he probably wants protect his partners independence.
Or he wants his partner to find love again if something happens to him (considering he literally almost died not even a year ago) .
Only 2 people who could've killed Cain are either Agio or Cain, because they are gods. Even when Agio killed humans Cain could revive them. When Ver killed humans and Vampires Cain could revive them. Only way Cain could die is if Agio, the god of night/death killed him OR if Cain killed himself somehow