Pokemon GO Leader Cliff is one of the Team Rocket heads you'll encounter on your journey to free your local PokeStops from their antagonistic influence.
There are several Team Rocket Leaders—also known as "Executives"—trainers can battle while re-capturing PokeStops in their neighborhood. Cliff, along with Sierra, Arlo, and boss Giovanni, appear at affected stops and are much more difficult to take down than their Grunt subordinates. Each one uses a specific handful of Pokemon that is subject change with every battle you face them in. Fortunately, these battle teams all come from the same pool.
Pokemon GO Leader Cliff
Cliff has the same chance of encounter as the rest of his colleagues. He is meant to be a direct counter to Team Mystic's Blanche. Like other Executives, he has a team of three Pokemon he will send out with the last being a Shadow Pokemon.
The first Pokemon will always be Cliff's Pinsir. No matter where you find him or how many times you challenge him, he will always start with Pinsir.
The second Pokemon on his team can be Marowak, Omastar, or Electivire. None of these choices have a higher chance to be used than the other, but, fortunately, the counters for each are similar enough that players likely won't have to worry too badly.
His third Pokemon will be Swampert, Tyranitar, or Torterra. Here is where the choice may get difficult, as Torterra doesn't share a lot of counter-types with Swampert or Tyranitar.
Fortunately, if players choose the wrong counter Pokemon for their team or simply can't push through, Cliff can be re-challenged as many times as it takes to win.