Question

the people regarded him as an important and called him a villain

Answer 1

The answer is given below, followed by explanation:

He was regarded as an imposter and called a villain by the people.

The active verb form in the given sentence was in Simple Past Tense (The people regarded him as an imposter). So following the steps and rules of active-passive formation, we made the passive (He was regarded as an imposter), and then added the other clause (and called a villain).

Answer 2

Answer:

He was regarded as an imposter and called a villain by the people