You Do Need power plug adapter while traveling from Réunion to Brazil.

Here is Why You Need An Adapter

The outlet and plug type used in Brazil are C and N and in Réunion are C and E. This is how they look like.

Réunion

In Réunion, outlets of type C and E are in use.

Type C

Type E

Brazil

In Brazil, outlets of type C and N are in use.

Type C

Type N