TM76 Struggle Bug is obtained right after you beat the Castelia City Gym. After defeating Gym Leader Burgh at the Castelia gym, he’ll give you the TM as a reward
You can first reach Castelia City after earning your Basic Badge in Nacrene City and crossing the Skyarrow Bridge. Burgh’s Gym is located in the far-west end of the city.
As for the move itself:
Struggle Bug is a Bug-type attack that deals poor damage at 30 base Power. The move also lowers its target’s Special Attack by one stage.
TM76 Struggle Bug Location
Step 1: Starting at the entrance to Castelia City, head west on the main road.
Step 2: Continue west on the road, passing the city’s Pokémon Center.
Step 3: Just ahead you’ll spot a large brown building with green trim. Keep west past this building.
Step 4: Stay west on the road, passing the blue sign.
Step 5: Once you get to the very end of this road (with guard rails to the western edge), turn and head north down the alley nearby.
Step 6: This alley exits onto a much larger road.
Take your first available right into the building with the Poke ball symbol to enter the Castelia City Gym.
Step 7: After defeating the Gym, Burgh will give you TM76 Struggle Bug.
Struggle Bug Details + Uses
|Struggle Bug Move Details|
Struggle Bug is a Special Bug-type attack that offers poor damage at 30 base Power. It does lower the target’s Special Attack by one stage, but that alone doesn’t justify using an attack that’s this weak in-game.
Take a look at the chart below to get an idea of how Special Attack is affected by stage:
Pitiful damage aside, it is worth mentioning that Struggle Bug is the only Technical Machine in Black or White that lowers the target’s Special Attack.
However, much more accessible moves like Light Screen will boost your Special Defense versus all Pokémon, which effectively accomplishes the same result.
So in general it’s really not worth using Struggle Bug at all, unless you have a specific strategy in mind for the move.