HP: 60 / Atk: 45 / Def: 110 / SAtk: 80 / SDef: 120 / Spe: 90
Swarm: Boost Bug moves 50% when below 33% health
Frisk: Tells you what item opponent has upon entering battle
Telepathy (Hidden): Can't be hurt by teammate attacks in a double battle
Moves worth Noting (Bold=Offensive Underlined=Status):
Stored Power is now a TM, but there aren't a whole lot of Pokemon out there that can reliably use it, or at least prefer the more reliable and convenient Psychic. But Orbeetle looks like a Pokemon that was specifically designed to utilize Stored Power to its full potential (Provided you can deal with the pain of evolving it). With access to reliable recovery, good defenses, fairly good speed, a couple of boosting moves, and a perfect secondary STAB, this UFO ladybug renders Ledian completely obsolete in every foreseeable capacity. Not sure if this will be enough to raise Orbeetle to OU, but only the playtesters will know that for sure.
+Built around effective Stored Power synergy with 3 notable boosting moves in Calm Mind, Agility, and Iron Defense
+Has a Bug STAB that offers a counter to Dark types that block nearly every other Stored Power set (Hatterene being a notable exception with its Fairy STAB)
+60/110/120 defenses make it able to take a hit well, and it has access to Recover to keep it healthy
+90 Speed is surprisingly fast for a defensive Pokemon, giving it a distinct advantage over similar walls
+Access to a few nifty utility moves like Hypnosis and the coveted entry hazard move Sticky Thread which lowers the opponents speed on the switch
-Bug/Psychic is not ideal defensive typing taking super effective damage from Fire, Flying, Bug, Rock, Ghost, and Dark attacks
-Lacks a means to effectively damage Steel types without several boosts in tangent with Stored Power
-Easily shut down by fast Taunt users that block access to its stat boost moves, Recover, and Baton Pass.
-4 moveslot syndrome keeps every set from being completely fool-proof
-None of its abilities are particularly useful under most circumstances
Despite getting its own Gigantamax Form (And a cool looking UFO one at that!), Orbeetle is not the best user of the Dynamax feature. Too many of its moves are status based so Max Guard can only take you so far, although the temporary HP increase is certainly welcome after you have gotten in enough stat boosts. The Sp. Att. drop from the Bug-Max move is not that useful, Psychic-Max is nifty for temporarily boosting Psychic moves and preventing priority moves, and its signature G-Max Gravitas is more useful in doubles than singles (It has no low accuracy moves or ground attacks to make use of the increased gravity)
Calm Mind + STAB's
EV's: (HP 252) (Defense 252) (Sp. Def 4)
Set up with Calm Mind to boost your special attack and special defense, use Recover accordingly to make sure you stay healthy at least long enough to get 2 boosts. With those two boosts Stored Power has a respectable base power of 100 before STAB. For every boost after that you get an extra 40 damage (100>140>180>etc) which is some serious damage not even accounting for the special attack boosts. The last move goes to either Bug Buzz or Baton Pass. Bug Buzz offers coveted coverage against other Psychic types that resist Stored Power but most notably hits Dark types for super effective coverage that would otherwise laugh at most other Stored Power sets. In terms of ability choice, seeing your opponents items with Frisk to read their strategy is the best option you have since you really don't want Orbeetle below 33% health for Swarm even if Bug Buzz gets boosted, and Telepathy is only really useful in doubles sets. Nature and EV's are pumped into HP and Defense since Calm Mind has you covered on the special defense side.
Calm Mind + Iron Defense
EV's: (HP 252) (Def 100) (Sp. Def 156)
Same set as above but with an added stat booster. Between the physical defense boost granted by Iron Defense and the special defense boost from Calm Mind, Orbeetle has the potential to become completely unbreakable without the likes of Toxic, phazing moves, or Perish Song. Heal damage as it come with Recover and decimate the opposition with boosted Stored Power. However this set's Achilles heel is that Dark types completely block it. Stored Power cannot bypass a Dark type's immunity which means you will either be forced to switch out or play a battle of attrition with PP and hope the opponent has low PP moves.
I am sure there are plenty of other sets you all can come up with, because Orbeetle is nothing if not versatile. This is my first go at creating one of these new competitive posts, so I hope I didn't screw up too badly...but after everything I've written, I'm sure I've at least convinced myself that Orbeetle is a worthy option in the competitive scene.