"Had been" is the past perfect tense of be.
Existed is the past tense. The past perfect tense is had existed.
The past tense of sit is sat; the past perfect tense is had sat.
The past tense is bled, and the past perfect tense is had bled.
Perfected is the past tense of perfect.
The past perfect tense of 'get' is 'had gotten'
The past perfect tense of do is had done.
present tense past tense future tense present perfect tense past perfect tense future perfect tense present progressive tense past progressive tense future progressive tense present perfect progressive tense past perfect progressive tense future perfect progressive tense
The past tense of paint is painted. Had painted is the past perfect tense.
Present tense, past tense, future tense, future perfect tense, present perfect tense and past perfect tense.
The past perfect tense is had added.
The past perfect tense is had burned.
The past perfect tense is "had learned".