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

Here is Why You Need An Adapter

The outlet and plug type used in Switzerland are C and J 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

Switzerland

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

Type C

Type J