Final answer:
The Praetorian Guard member responsible for imprisoning Agrippina and other enemies of Tiberius was Sejanus.
Step-by-step explanation:
The Praetorian Guard member who was the responsible for putting Agrippina in prison and dealing with other enemies of Emperor Tiberius was the Sejanus.
As the head of the Praetorian Guard, Sejanus held the significant power in Rome and was a close ally of Tiberius until he fell from the grace.
Sejanus's role in the political intrigues during the Tiberius's reign was significant, and his actions had far-reaching consequences, particularly after he was executed for treason, which had revealed his conspiracy against Tiberius.