Power Greninja 3.0 Greninja - PokeGamerBoy17

Guide

This is a high-skill damage-dealing build that best uses Greninja's natural healing ability to stay in battle longer.

Before I start, I need to explain a couple things.
First, the basic attack is special because it has both a melee and a ranged attack. When ranged, it reduces the cooldown of Bubble or Water Shuriken (or Surf if you're playing that build) by 0.5 seconds and boosted attacks reduce enemy movement speed by 25% for 0.5 seconds. When melee, it deals bonus damage equal to 5% missing HP (calculated as basic attack damage and subject to basic attack effects). Boosted melee attacks also dash through the primary target and increases the missing HP damage to 10%. The melee attack also deals damage in a small area of effect.
Next, Greninja's healing mechanic allows it to heal with every basic attack it uses. With a Lifesteal stat of 15% (level 13+), you heal 15% of any basic attack damage you deal, no matter what. When combined with all 3 held items this build uses, that can be a good chunk of healing.

Now, onto the build guide.

Start with Bubble and go around the wall to the central area. You can also just barely roll through the wall with Substitute when timed correctly.
Alternatively, you can start with Bubble and take bottom path (Attack Weight instead of Muscle Band in this case is also good). Any option is viable.

Once you have some Aeos Energy, try to start scoring goals so to max out the Attack Weight as soon as possible.

Double Team has a special mechanic where the clones will attack for you. They have the same stats as you, but they take 500% damage and deal 18% damage. However, this is still very good. The clones will automatically target the nearest opponent or wild Pokémon and attack with Bubble or Water Shuriken. They will disappear after 3 seconds, though, so be careful when you use it.

Once you get Water Shuriken, the real fun begins. You can start dealing massive damage quickly and stay alive if you played the early game right. This is also where your held items will come into play the most.

Scope Lens adds onto Greninja's base crit-rate of 30% (level 9+), which can make for some deadly, half-health-killing single basic attacks. (Yes, I've done this and it's insane.)

Rapid-Fire Scarf just adds onto literally everything Greninja is good at. If you're not using Rapid-Fire Scarf on Greninja, you'd better have a really good reason. This item simply boosts basic attack speed for a short time after three basic attacks. Greninja lives basic attacks. Combining Greninja's dual basic attack mechanic, its high Lifesteal stat, and the Muscle Band and Scope Lens, Rapid-Fire Scarf is just too broken not to use.

After learning that X Attack does not get the broken buffs I thought I did, I resorted to ol' reliable, the Eject Button. It's a classic escape plan that works as well as ever.

Brown and black boost emblems are best for attack and cooldown reduction. I tried using red, but I couldn't get enough to make it worth it.