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