Complete the evolution
Learn Vine Whip, raise it to level 5 and take the Power run stat card at least once. The ready evolution is included in a level-up offer; select it to turn Vine Whip into Power Whip. It keeps its grass type and melee behavior.
Read the stat change
The comparison below applies the official behavior ladder and evolution modifiers. Values are before partner attack, permanent/run modifiers, type matchup, weather and actual hit contact. A multi-hit pattern is not guaranteed single-target damage.
If you are stuck
At level four, you still need one move upgrade. At level five without Power, take that stat card; a menu upgrade does not count. If already evolved, there is no second evolution in this snapshot. Check the current move in the evolution checker.