You Do Need power plug adapter while traveling from Niue to Saint Kitts and Nevis.

Here is Why You Need An Adapter

The outlet and plug type used in Saint Kitts and Nevis are D and G and in Niue is I. This is how they look like.

Niue

In Niue, outlets of type I are in use.

Type I

Saint Kitts and Nevis

In Saint Kitts and Nevis, outlets of type D and G are in use.

Type D

Type G