This is Reachzero's set. I saw him talking about it and decided to try it. It's pretty amazing and idk why it isn't on site already :\
[SET]
name: Offensive
move 1: Tri Attack
move 2: Ice Beam
move 3: Discharge
move 4: Recover
item: Eviolite
ability: Download
nature: Modest
evs: 252 HP / 4 Def / 252 SpA
[SET COMMENTS]
<p>Because Porygon2's defenses are so fantastic with Eviolite, its offensive potential seems to have been overlooked. Offensive Porygon2 is amazing, and is capable of beating a significant portion of UU. With access to the infamous BoltBeam combination, a strong STAB move in Tri Attack, and a fantastic ability in Download, there really aren't many Pokemon that can safely switch into this little duck. Download gives Porygon2 a chance to raise its surprisingly high base 105 Special Attack stat by one stage whenever it switches into an opponent with a lower Special Defense stat than Defense. Porygon2 gets a Special Attack boost from many common Pokemon in UU such as Rhyperior, Nidoking, Donphan, Suicune, Slowbro and Blastoise, meaning it will often receive the appropriate boost. Despite the offensive nature of this set, Porygon2 is still incredibly bulky. Pair that with Eviolite and Recover, and it's incredibly difficult to take down unless your opponent has a strong Fighting-type, such as Heracross, Machamp, or Cobalion. Porygon2 is a perfect candidate for a bulky offense team, as it can sponge hits from the likes of Nidoking with ease, and dish out massive damage. To showcase just how great Porygon2 is, here are some damage calculations to demonstrate its power after a Download boost:</p>
<ul class="damage_calculation">
<li>+1 Tri Attack vs 252 HP / 0 SpD Machamp: 54.9% - 65.1%</li>
<li>+1 Tri Attack vs 4 HP / 0 SpD Heracross: 64.6% - 75.8%</li>
<li>+1 Tri Attack vs 252 HP / 0 SpD Hitmontop: 56.3% - 66.4%</li>
<li>+1 Discharge vs 252 HP / 4 SpD Suicune: 54% - 63.9%</li>
<li>+1 Discharge vs 252 HP / 4 SpD Slowbro: 75.1% - 88.8%</li>
<li>+1 Discharge vs 252 HP / 4 SpD Blastoise: 65.7% - 77.3%</li>
<li>+1 Discharge vs 252 HP / 252 SpD Empoleon: 47.8% - 56.5%</li>
<li>+1 Ice Beam vs 160 HP / 0 SpD Rhyperior: 86.4% - 101.7%</li>
<li>+1 Ice Beam vs252 HP / 136 Spd Roserade: 69.8% - 82.1%</li>
<li>+1 Ice Beam vs 248 HP / 228 SpD Zapdos: 60.6% - 71.5%</li>
</ul>
[ADDITIONAL COMMENTS]
<p>The EVs are very straightforward: 252 HP EVs gives Porygon2 its signature bulk, while 252 EVs in Special Attack along with a Modest nature maximizes its damage output. Eviolite is truly a blessing for Porygon2, as it raises its defenses from great to fantastic. Thunderbolt is an option over Discharge, although the power difference is slight and the higher paralysis chance of Discharge is preferred. Charge Beam is also a viable option, as it lets Porygon2 attempt to further boost its Special Attack stat. While Download is the preferred ability for this set, all three of its abilites are usable. Trace can be used if you want to shut down things like SubCM Chandelure and have a decent switch-in to Flash Fire Pokemon in general. It also lets Porygon2 switch into things like Chansey and Roserade without having to worry about the statuses they dish out. Analytic can give you a 30% boost if you move last, which means that it is a safer but weaker option compared to Download. If you're using Analytic, then use Thunderbolt and not Discharge, as the higher paralysis chance is counterproductive. Snorlax, Chansey, specially defensive Escavalier and other specially defensive Pokemon can be annoying, but can only beat Porygon2 with Toxic. Fighting-type Pokemon such as Cobalion, Heracross, Machamp and Hitmontop will still give the cyber duck trouble, but they'll have to think twice before switching in on a Tri Attack. Offensive beasts such as Alakazam can clean up after the massacre that Porygon2 leaves behind. A Pokemon such as Gligar can make a valuable teammate since it can sponge strong Fighting-type attacks. It can also shut down the aforementioned specially defensive Pokemon with a combination of Taunt, Roost, and Earthquake.</p>
