I could kill you could kill he could kill we could kill you could kill they could kill
V-ing form
I could be killing you could be killing he could be killing we could be killing you could be killing they could be killing
Perfect
I could have killed you could have killed he could have killed we could have killed you could have killed they could have killed
V-ing perfect
I could have been killing you could have been killing he could have been killing we could have been killing you could have been killing they could have been killing
Negation
Simple form
I couldn't kill you couldn't kill he couldn't kill we couldn't kill you couldn't kill they couldn't kill
V-ing form
I couldn't be killing you couldn't be killing he couldn't be killing we couldn't be killing you couldn't be killing they couldn't be killing
Perfect
I couldn't have killed you couldn't have killed he couldn't have killed we couldn't have killed you couldn't have killed they couldn't have killed
V-ing perfect
I couldn't have been killing you couldn't have been killing he couldn't have been killing we couldn't have been killing you couldn't have been killing they couldn't have been killing
Interrogative form
Simple form
could I kill? could you kill? could he kill? could we kill? could you kill? could they kill?
V-ing form
could I be killing? could you be killing? could he be killing? could we be killing? could you be killing? could they be killing?
Perfect
could I have killed? could you have killed? could he have killed? could we have killed? could you have killed? could they have killed?
V-ing perfect
could I have been killing? could you have been killing? could he have been killing? could we have been killing? could you have been killing? could they have been killing?
Interro-negative form
Simple form
couldn't I kill? couldn't you kill? couldn't he kill? couldn't we kill? couldn't you kill? couldn't they kill?
V-ing form
couldn't I be killing? couldn't you be killing? couldn't he be killing? couldn't we be killing? couldn't you be killing? couldn't they be killing?
Perfect
couldn't I have killed? couldn't you have killed? couldn't he have killed? couldn't we have killed? couldn't you have killed? couldn't they have killed?
V-ing perfect
couldn't I have been killing? couldn't you have been killing? couldn't he have been killing? couldn't we have been killing? couldn't you have been killing? couldn't they have been killing?