Gen 9 National Dex UU Booster Energy: Speed
Iron Boulder @ Booster Energy
Ability: Quark Drive
Tera Type: Rock
EVs: 100 HP / 156 Atk / 252 Spe
Adamant Nature
- Swords Dance
- Mighty Cleave
- Close Combat / Zen Headbutt / Megahorn
- Earthquake / Zen Headbutt
A Booster Energy: Speed set Iron Boulder can use in NatDex UU. I'm aware Anchor9 already posted a Booster Energy: Speed, but this set version I'm posting has some different things to it. One being an additional coverage option, and most importantly, the EV spread and Nature. Iron Boulder can afford to use Adamant Nature in NatDex UU since you outspeed all the relevant Choice Scarf Pokemon bar Serperior. You also live a +1 Energy Ball from Booster Energy: Speed Iron Moth if you're at full HP if you're concerned about that.
Swords Dance lets Iron Boulder be a potent sweeper once its checks are weakened or taken out. Mighty Cleave is Iron Boulder's reliable STAB, being able to ignore Protect, which is nice against Pokemon such as Celesteela since they can get hit if they try to use Protect to scout Iron Boulder. Close Combat allows Iron Boulder to hit Steel-types such as Excadrill, Bisharp, Magnezone, as well as Pokemon such as Ting-Lu and Ursaluna super effectively. Earthquake also allows Iron Boulder to hit the mentioned Steel-types as well as Aegislash. Earthquake also lets Iron Boulder hit opposing Iron Boulder super effectively and can be used to hit Pokemon Close Combat would hit if Iron Boulder can't afford the defense drops. Zen Headbutt is an option to be able hit Fighting- and Poison-types such as Amoonguss, Buzzwole, and Keldeo super effectively. Megahorn is an option to OHKO Hydrapple after a Swords Dance boost. Megahorn also allows Iron Boulder to hit Ting-Lu super effectively, as well as hitting Pokemon such as Slowbro and Mega Latias a bit harder than Mighty Cleave. If you use Megahorn, I recommend having Earthquake as the last slot so you can have a way to hit Steel-types such as Aegislash, Magnezone, and Excadrill.
156 Attack EVs with an Adamant Nature gives Iron Boulder as much power as possible while making sure Iron Boulder gets a speed boost from Booster Energy provided Sticky Web isn't on your side. The rest of the EVs are used in HP to give Iron Boulder some bulk. The bulk on Iron Boulder is really nice to survive attacks it otherwise wouldn't. For example, when at full HP, Iron Boulder can use Swords Dance as a Ting-Lu switches in, then use Swords Dance again if your opponent doesn't know you have the HP EVs and decides to go for Earthquake instead of Whirlwind, as the bulk prevents Ting-Lu's Earthquake from OHKOing Iron Boulder from full HP:
0 Atk Ting-Lu Earthquake vs. 100 HP / 0 Def Iron Boulder: 282-332 (81.5 - 95.9%) -- guaranteed 2HKO
I recommend using this set on HO teams with Lead Mew, as lead Mew can cripple physical wallbreakers with burns, which can create more setup opportunities for Iron Boulder, as well as setting up hazards to put opposing Pokemon in range of Iron Boulder's attacks.
