to do it to/for him, her, or them, to make him, or them understand it
Tengo que hacérselo entender.
I have to make him understand.
— Cinema Paradiso (1988)
Debes hacérselo.
You should do it.
¿Por qué tenían que hacérselo a ellos?
Why did they have to do that to them?
— Кин-дза-дза! (1986)
¿Quieres hacérselo?
Do you want to do it to him?
— Paris, je t'aime (2006)