Tiberius wasn’t a monster. Caligula was a power-mad youngster and Nero was a monster.
They don’t have any parallels with Stalin, Mao or Hitler.
Stalin, Mao and Hitler have parallels with the great centralized states of the Bronze age or early Iron age.
Tiberius entertained himself by molesting children sexually and then tossing them off the cliffs of the Isle of Capri. At the cliff bottom, men in boats killed any who survived. That was only one of his hobbies. Of course Tiberius was a monster. As he raised Caligula, he famously said, "I am nursing a viper for the Roman People."
Caligula was probably psychotic.
Their parallels to Stalin, Mao, and Hitler are striking.
There have been other monsters. There are today. There will be in the future. Decent people must control them and prevent them from acquiring great power.