0658 Greninja

Water Shuriken boasts by far the greatest energy generation and is Greninja's preferred Fast Attack. Bubble deals very slightly more damage for considerably less energy gain, making it undesirable. Feint Attack is mediocre all around despite providing extra Dark-type damage.

Night Slash costs the least amount of energy, benefits from STAB, can be used frequently, and has a small chance to proc its self-buff. Hydro Cannon is an excellent STAB move and can be fired rapidly thanks to Water Shuriken's insane energy generation. Surf is a good move, but is strictly inferior to Hydro Cannon as it deals less damage for the same energy cost. Aerial Ace is quite underwhelming; its coverage against Greninja's weaknesses is likely not enough given its poor damage and greater energy cost. Hydro Pump demands too much energy to use. 

Greninja shares the same Water/Dark typing as Sharpedo, with similarly high offensive stats and fragile bulk. Fortunately for Greninja its moveset is a lot faster and more efficient, with greater energy generation and more frequent shield pressure. With Water Shuriken's energy generation and Hydro Cannon's extremely strong parameters, Greninja is an incredibly potent sweeper. It outpaces most Pokemon's Charged Attacks and can often beat them in CMP. The aforementioned quality combined with Greninja's reliance on Charged Attacks to do most of its damage means that energy management is key to maximizing Greninja's potential.

Greninja's frailty means that it relies heavily on shields to succeed. Investing in shields for Greninja allows it to smash apart several great league staples such as Registeel, Sableye, and Lickitung. Since it relies on shields, Greninja's worst enemy is high Fast Attack pressure - Dragon Breath, Counter, Razor Leaf, Charm, Vine Whip, and so on. High Fast Attack pressure Pokemon such as Altaria, Medicham, Shadow Victreebel, and any Charmer will make short work of Greninja, invalidating shields reserved for it. Azumarill is another roadblock for Greninja due to its immense bulk and resistance to Greninja's STABs.

Greninja's sweeping potential still remains in this league, but it must now note that everything (including itself) is slightly tankier compared to Great League. On one hand, Greninja becomes slightly less shield dependent (it still is), but on the other hand, it won't be dousing its competitions as quickly. In terms of threats, Greninja no longer has to worry about Medicham, Altaria, or Azumarill, but it must now wary of Cobalion and Virizion. These two bulky Fighting-type Legendary Pokemon can keep up in pace with Greninja's spammy Hydro Cannons thanks to their equally spammy Double Kick + Sacred Sword combo. Virizion in particular resists both of Greninja's STABs, making it Greninja's nemesis.

Greninja desperately needs stats, especially bulk, if it's to compete in Master League. Feint Attack helps win the Metagross matchup, but the rest of the meta will be a major challenge.