Question

he was the last man to arrive here
( change into complex sentence)

Answer 1

He confessed his crime. (Simple sentence)
He confessed that he was guilty. OR He confessed that he had committed a crime. (Complex sentence – here we expanded the noun ‘his crime’ into the noun clause ‘that he was guilty’ or ‘that he had committed a crime’)
He bought his uncle’s factory. (Simple sentence)
He bought the factory that belonged to his uncle. (Here we expanded the noun phrase ‘his uncle’s factory’ into the adjective clause ‘that belonged to his uncle’.)

Answer 2

He was the last man who arrived there