Can u one hit terapagos?

Maybe but try not to beat it early

"During the battle against Terapagos in its Stellar Form, if it is confused by a move such as Dynamic Punch and then breaks its own barrier due to confusion damage, the player can then knock out Terapagos early by dealing enough damage. If this happens, the game will put the battle in an unwinnable state, as the battle script has Terapagos create another barrier, but as its HP was effectively depleted, it is no longer recognized as an active participant of the battle."