You Do Need power plug adapter while traveling from Liechtenstein to South Sudan.

Here is Why You Need An Adapter

The outlet and plug type used in South Sudan are C and D and in Liechtenstein are C and J. This is how they look like.

Liechtenstein

In Liechtenstein, outlets of type C and J are in use.

Type C

Type J

South Sudan

In South Sudan, outlets of type C and D are in use.

Type C

Type D