So, this is my first time posting anything of any kind of substance in these forums so I apologize in advance if I did something wrong.
Pokemon Name: Meganium
Moveset Name: Offensive Screens
Move 1: Reflect/Light Screen
Move 2: Leaf Storm
Move 3: Hidden Power [Rock]/Hidden Power [Ice]
Move 4: Energy Ball/Aromatherapy/Synthesis
Item: Life Orb
Ability: Overgrow
Nature: Modest
EVs: 252 HP/252 SpA/4Spe
This is one of those off the beaten path sets that doesn't make much sense at first glance. Meganium is a good Pokemon, a very good Pokemon in fact, but the poor thing gets outclassed by so much that it's not even funny. Most notably, Venusaur, the top UU Poke, eclipses her in almost every way. Still, she does have some niches she can carve for herself. Also, her analysis is one of the most outdated ones on the site, I think
This set has two purposes, the main purpose is to set up Screens support to aid her teammates. The secondary goal is to attempt a sweep from the safety of her own barriers. Grass is an excellent STAB to have in this metagame and Meganium gets access to Leaf Storm, which she's no slouch at using.
The idea here is to come in on something it can scare off, like Milotic, and set up one of the screens on the switch. The barrier you choose should depend on what you need your team to cover more. Each screen is beneficial to Meganium in different scenarios, but more on that later. Behind the screen, you can then attempt to take out a counter with the corresponding Hidden Power. If she can't handle the counter, she switches out. If she takes out the counter, the next thing they send in is probably not going to like Leaf Storm. She can switch out after that as her bulk and typing will allow her more chances to switch back in should the need arise.
The choice between Hidden Power [Rock] and Hidden Power [Ice] largely depends on what you want to hit harder. HP Rock OHKO's all Moltres, Swellow and Scyther switching in even without Stealth Rock support while HP Ice 2HKO's all of the tier's Grass types bar Specially defensive Venusaur. They can't KO back fast enough if she's behind the corresponding screen.
The last slot depends on what your team requires. Energy Ball gives her a weaker yet more reliable STAB for when Leaf Storm is not necessary, Aromatherapy is to cure status for the entire team and Synthesis is a reliable healing move. Between entry hazards, Life Orb recoil and the damage she'll take even behind screens, Meganium can be worn out pretty fast so Synthesis is handy for keeping her alive.
Life Orb is the item of choice here to maximize her damage output and because, together with a Modest nature, it helps her net some kills she otherwise would miss, particularly with Leaf Storm. 252 SpA EVs is to capitalize on her offensive abilities since her Special Attack stat isn't spectacular. 252 HP give her enough bulk to survive many powerful attacks while she's behind the respective screens (more on that later too) and the last four are given to Spe so she can outrun Jolly Max Speed Rhyperior by one point.
This Meganium is above all else a team player. Stealth Rock support is necessary for netting some key KO's such as defensive Spiritomb, SD Leafeon and NP Mismagius. The Pokemon that wall this set (Arcanine, Houndoom, Drapion, Toxicroak and Registeel) are all weak to Ground so Rhyperior and Donphan make excellent partners for her. They fire off powerful STAB Earthquakes to get rid of her counters and in return she can take out the Water and Grass types that give them trouble. Donphan in particular can set up Stealth Rock and lure in Milotic.
Since Fire types are the bane of this Meganium's existence, she can have great synergy with offensive Pokemon like Arcanine, Houndoom and Feraligatr, all of whom can switch in with impunity on predicted Fire moves and neither of which enjoys dealing with Milotic (which Meganium OHKO's with Leaf Storm).
The best part about this set is that, even though it can effectively sweep on it's own merit, it's primary job is done when it sets up the screens. So if something she can't handle comes in, she can just switch out and come back later.
Anyway, here are some damage calcs to illustrate the sheer power of this set in both the offensive and defensive roles:
On the offensive:
-Modest LO Leaf Storm vs 248/0 Milotic=101.3%-119.6% (OHKO)
-Modest LO Leaf Storm vs 4/0 Mismagius=88.5%-104.6% (guaranteed OHKO with SR)
-Modest LO Leaf Storm vs 208/116 Spiritomb=62.8%-74.1% (2HKO with SR even after stat drop)
-Modest LO HP [Ice] vs 252/216 Altaria=64.4%-76.8% (2HKO)
-Modest LO HP [Ice] vs 0/0 Leafeon=84.9%-100.4% (guaranteed OHKO 100% of the time with SR and 1 layer of Spikes)
-Modest LO HP [Ice] vs 4/0 Sceptile=66%-78% (2HKO)
-Modest LO HP [Ice] vs 252/0 Tangrowth=69.3%-81.7% (2HKO)
-Modest LO HP [Ice] vs 212/0 Torterra=96.9%-114.6% (OHKO)
-Modest LO HP [Ice] vs 0/0 Venusaur=53.8%-63.8% (2HKO)
-Modest LO HP [Ice] vs 0/4 Swellow=105.7%-124.9% (Same with HP Rock)
-Modest LO HP [Rock] vs 248/0 Moltres=97.1%-114.9% (almost guaranteed OHKO. Offensive variants are OHKO'd 100% of the time)
-Modest LO HP [Rock] vs 0/4 Scyther=136.7%-162.3%
On the defensive:
Herein lies the choice between Reflect and Light Screen. Obviously she should go with the one your team needs more, but these damage calcs show how she fares agains several physical and special threats behind the respective screen:
Reflect
-Adamant CB Absol Night Slash vs Reflect Meganium=25.8%-30.8% (she can OHKO with LO Leaf Storm)
-Jolly CB Aggron Head Smash vs Reflect Meganium=44.8%-53% (She can OHKO with LO Leaf Storm)
-+1 Adamant LO Altaria Outrage vs Reflect Meganium=38.2%-45.3% (she can 2HKO with LO HP Ice)
-+2 Adamant Feraligatr LO Ice Punch vs Reflect Meganium=55.5%-65.4% (she can OHKO with Leaf Storm)
-Jolly Leafeon LO X-Scissor vs Reflect Meganium=28%-33.5% (she can 2HKO with HP Ice)
-Adamant CB Miltank Return vs Reflect Meganium=27.5%-32.4% (she can OHKO with Leaf Storm)
-Adamant LO Nidoking Megahorn vs Reflect Meganium=40.7%-48.4% (she can OHKO with Leaf Storm)
-+2 Jolly Sceptile X-Scissor vs Reflect Meganium=36.3%-42.9% (2HKO with HP Ice)
-Jolly LO Scyther Technician Bug Bite vs Reflect Meganium=46.7%-56% (survives and OHKO with HP Rock)
-+1 Jolly Swellow Brave Bird vs Reflect Meganium=61%-72.5% (survives and OHKO with HP Rock)
Light Screen
-Adamant Altaria LO Fire Blast vs LS Meganium=20.9%-24.7% (she 2HKO with HP Ice)
-Modest CS Alakazam Signal Beam vs LS Meganium=38.5%-45.6% (she can OHKO with Leaf Storm)
-Modest LO Ludicolo Ice Beam vs LS Meganium=31.3%-37.4% (Leaf Storm is a guaranteed KO with SR)
-Modest Specs Mestprit Ice Beam vs LS Meganium=40.1%-47.8%
-Timid Specs Milotic Ice Beam vs LS Meganium=35.7%-42.3% (she can OHKO with Leaf Storm)
-+2 Timid NP Mismagius Shadow Ball vs LS Meganium=30.8%-36.5% (at worst, she'll 2HKO with Leaf Storm and a second attack)
-LO Modest Moltres Fire Blast vs LS Meganium=74.2%-87.9% (can survive and OHKO with HP Rock, at worst, Life Orb takes it's toll
and they tie)
-Modest Specs Tangrowth HP Fire vs LS Meganium=30.8%-36.3% (she can 2HKO with HP Ice)
It should be noted that a physical variant with an Adamant nature and Seed Bomb, Return/Earthquake is viable. This set is not afraid of Arcanine or Houndoom as long as Stealth Rocks are on the field, but the power gap between Leaf Storm and Seed Bomb is quite noticable.
