Left is already in the past tense. It's the past tense of leave.
The past perfect tense of "leave" is "had left." It is formed by combining the past tense of "have" (had) with the past participle of "leave" (left).
Already is not a verb and does not have a past tense.
Past tense: left Present tense: leave Future tense: will leave
The past tense of "leave" is "left" and the past participle is also "left."
"Leave" is the present tense; "left" is the past tense and past participle.
"I was" is already in the past tense. "I am" is present tense.
Did not do it -> did not do it (same past tense form)
Wrote is past tense. It is the past tense of write.Wrote is already a past tense.
Could is already the past tense. It is the past tense of the verb "can".
Already is not a verb, so it does not have a past perfect tense.
Rumored is already the past tense.