None of the Regis can be described as great attackers. They’re at best decent but you really don’t and should not need to power them up or use them barring an extreme shortage of good Pokemon.
Please do not power this guy up. If you want to catch a lot of it, that’s up to you. It’s better off as a gym defender but as we know, Niantic says you can’t use legendaries as gym defenders. Regirock has 179 attack, 309 defence and 190 stamina. It’s more focused on taking damage than deal damage, not ideal at all for an attack. Just collect it, and keep it there.
|Resists||Weak To||Normal Damage|
As a pure Rock type, Regirock comes with 5 weaknesses, so plenty of counters to it. Just stick to those 5 types of attacks and you’ll take it down in no time.
Rock Throw with its STAB moves is going to be far more dangerous to Rock Smash, unless you’re using Steel types.
The same with the Fast moves, Stone Edge is the most dangerous thanks to STAB. Focus Blast is again, dangerous to Steel types so if you’re using them ,take note. Zap Cannon is also dangerous if you’re a Water type but other than that, it shouldn’t pose a problem.
Assembling The Team
With 5 weaknesses, you just need to ensure you don’t pick Steel types for a Focus Blast Regirock or Water types for a Zap Cannon Regirock.
Metagross is the best Steel type attacker in the game. Its also an exception to being weak to Focus Blast, its Steel/Psychic typing cancelling out that weakness to Fighting. It also resists Stone Edge thanks to being Steel.
For Metagross, use the Community Day exclusive moveset of Bullet Punch and Meteor Mash. Bullet Punch is a fast move available outside of Community Day but Meteor Mash currently is only available in Community Day events so there’s way of getting it unless you trade with other players.
The best Ground type attacker, Groudon also resists Regirock’s Rock and Electric moves. For moves you won’t be using Earthquake, Solarbeam actually does more damage overall. For its fast move, go with Mud Shot.
The best Water type out there, Kyogre is the hardest hitting one. Just watch out for Zap Cannon. Other than Zap Cannon, Kyogre can be used without too many problems. For moves, go with Waterfall and Hydro Pump.
Dialga needs to watch out for Focus Blast but other than that, it resists the other moves of Regirock. Rock Smash is also a problem but its a Fast Move so you don’t need to worry too much about it. For moves, go with Metal Claw and Iron Head.
Its part of a very mediocre trio that’s best left to collect and nothing else. The legendary titans were powerful tanks in the core games but here the only things they have in common are being weak in attack and a weakness to Fighting.