Past perfect is had + past participle.
Because realize is a regular verb the past participle is realized ( plus ed )
had realized.
I had realized my mistake when the alarm went off.
"Had awoken" is the past perfect tense.
The past perfect tense is 'had started'.
The past perfect tense of begin is had begun.
The past perfect tense of wake is had woken.
The past perfect tense of creep is had crept.
The past tense of "realize" would be "realized".
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 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.
The past perfect tense of "learn" is "had learned."