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