Had proven.
The past perfect tense of hope is had hoped.
"Had been" is the past perfect tense of be.
The past perfect tense is had broken.
The past perfect tense is had met.
The past perfect tense is had borne.
The present perfect tense of "proven" is: "I had proven". It combines the present in the past tense.
Existed is the past tense. The past perfect tense is had existed.
The past tense is bled, and the past perfect tense is had bled.
The past tense of sit is sat; the past perfect tense is had sat.
The past tense of "prove" is "proved" in British English and "proven" in American English.
The past perfect tense of hope is had hoped.
The past perfect tense is had set.
The past perfect tense is had submitted.
The past perfect tense is "had confronted".
The past perfect tense is had rung.
The past perfect tense is had burned.
The past perfect tense is had chosen.