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

Here is Why You Need An Adapter

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

Argentina

In Argentina, outlets of type C and I are in use.

Type C

Type I

Swaziland

In Swaziland, outlets of type M are in use.

Type M