When I use one of my opponent's Pokemon's non-GX attacks with Malamar's "Hypnotic Reign", do I need to have the energy required in order to use that attack?
No you do not, but you need to do any necessary effects such as discarding Energy.
Source: Unbroken Bonds FAQ (2019-04-19), TPCi Rules Team (2019-05-02)

Relevant cards

Note: All applicable cards may not be listed below.
SM10_119
SM10_119