Pokémon had no moves left with plenty of PP
This is a valid strategy which forces the Pokemon to use struggle every other turn.
As answered on Pokemon Database Torment & Encore, it goes to say:
Encore+Torment would simply make the pokemon struggle every alternate turn, because Torment says they can't use the same move twice in a row, while Encore prevents them from using a different move, so they have to use Struggle.
If you wish to use this strategy yourself, Pokemon Database contains a list of Pokemon that are able to learn both Torment/Disable and Encore
Torment & Encore
- Abra
- Kadabra
- Alakazam
- Mr. Mime
- Ralts
- Kirlia
- Gardevoir
- Chimchar
- Monferno
- Infernape
- Mime Jr.
- Chatot
- Gallade
- Purrloin
- Liepard
- Darmanitan
- Hawlucha
Disable & Encore
- Psyduck
- Golduck
- Kadabra
- Alakazam
- Seel
- Dewgong
- Ralts
- Kirlia
- Gardevoir
- Spinda
- Gallade