Answer:
A modern day leader can use physical and psychological violence, remove an individual and collective liberties from citizens, create fear and establish a government based on totalitarianism (meaning-a system of government that is centralized and dictatorial and requires complete subservience to the state).
Step-by-step explanation:
To control a population, a modern-leader can base his government on physical and psychological violence. (not a great way if you ask me!) The leader can exercise constant and permanent vigilance over the life of the citizens, controlling even the personal and family life of certain people, that is, an extreme and excessive case of authoritarianism.
In addition, this leader can end the freedom of the population, establish a strong restriction in the media, among other many other things.