Could? Yes, what with over twenty legally lethal weapons in this room alone, and many more throughout my home, along with anything improvised, or even bare-handed, indeed. I have the physical capacity to kill someone.
Would?
Without thought, if they:
Broke in
Stole something
Threatened anyone with severe injury who I wouldn't have
Threatened my loved ones/family/friends/pets.
Blackmailed anyone I wouldn't have.
Beat up someone I wouldn't have.
...
Basically, fuck with someone I would let be, you will not walk away.
I may die, but fuck all, you'll be dragged down to Hell with me.