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

Here is Why You Need An Adapter

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

Swaziland

In Swaziland, outlets of type M are in use.

Type M

Brazil

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

Type C

Type N