Warning, this verb may not exist. Conjugation is given as example.
Affirmation
Simple form
I could regret regret you could regret regret she could regret regret we could regret regret you could regret regret they could regret regret
V-ing form
I could be regret regreting you could be regret regreting she could be regret regreting we could be regret regreting you could be regret regreting they could be regret regreting
Perfect
I could have regret regreted you could have regret regreted she could have regret regreted we could have regret regreted you could have regret regreted they could have regret regreted
V-ing perfect
I could have been regret regreting you could have been regret regreting she could have been regret regreting we could have been regret regreting you could have been regret regreting they could have been regret regreting
Negation
Simple form
I could not regret regret you could not regret regret she could not regret regret we could not regret regret you could not regret regret they could not regret regret
V-ing form
I could not be regret regreting you could not be regret regreting she could not be regret regreting we could not be regret regreting you could not be regret regreting they could not be regret regreting
Perfect
I could not have regret regreted you could not have regret regreted she could not have regret regreted we could not have regret regreted you could not have regret regreted they could not have regret regreted
V-ing perfect
I could not have been regret regreting you could not have been regret regreting she could not have been regret regreting we could not have been regret regreting you could not have been regret regreting they could not have been regret regreting
Interrogative form
Simple form
could I regret regret? could you regret regret? could she regret regret? could we regret regret? could you regret regret? could they regret regret?
V-ing form
could I be regret regreting? could you be regret regreting? could she be regret regreting? could we be regret regreting? could you be regret regreting? could they be regret regreting?
Perfect
could I have regret regreted? could you have regret regreted? could she have regret regreted? could we have regret regreted? could you have regret regreted? could they have regret regreted?
V-ing perfect
could I have been regret regreting? could you have been regret regreting? could she have been regret regreting? could we have been regret regreting? could you have been regret regreting? could they have been regret regreting?
Interro-negative form
Simple form
could I not regret regret? could you not regret regret? could she not regret regret? could we not regret regret? could you not regret regret? could they not regret regret?
V-ing form
could I not be regret regreting? could you not be regret regreting? could she not be regret regreting? could we not be regret regreting? could you not be regret regreting? could they not be regret regreting?
Perfect
could I not have regret regreted? could you not have regret regreted? could she not have regret regreted? could we not have regret regreted? could you not have regret regreted? could they not have regret regreted?
V-ing perfect
could I not have been regret regreting? could you not have been regret regreting? could she not have been regret regreting? could we not have been regret regreting? could you not have been regret regreting? could they not have been regret regreting?