The Colossal Discovery Special Research is likely wrapped up for players purchased a ticket to that event, but that doesn't mean that Regigigas is gone forever. The latest Legendary to arrive in Pokemon GO was only available through the exclusive Special Research originally, but now players are able to earn an EX Raid invite to encounter the big creature.
Regigigas is a pretty challenging Pokemon GO raid and players will definitely want to make sure they've taken some time to do a little research and power up the right kind of team before heading out and cashing in their EX Raid ticket. Hopefully players have plenty of people showing up to their Raids, but even in those cases, it'll still help to have the right roster ready to fight.
Regigigas counters are mostly going to be the most powerful Fighting-types in the game. This isn't the first popular Raid Boss to be weak against Fighting-types, which means that many players should already have spent some Stardust and Candy powering up a strong counter roster for this type of situation. Hopfully catching some of the most powerful Pokemon from the Unova region is about to pay off...
Best Regigigas Counters
Machamp - Counter/Dynamic Punch
Hariyama - Counter/Dynamic Punch
Blaziken - Counter/Focus Blast
Mewtwo - Confusion/Focus Blast
Emboar - Low Kick/Focus Blast
Heracross - Counter/Close Combat
Lucario - Counter/Close Combat
Toxicroak - Counter/Dynamic Punch
Metagross - Bullet Punch/Meteor Mash
Breloom - Counter/Dynamic Punch
Regigigas is a very exciting addition to the metagame and a fun new Pokedex entry, so trainers won't want to miss this limited opportunity to head out and battle against the Pokemon. Keep in mind that you'll need to have earned an EX Raid Invite or have a friend with a guest ticket they can give you.
Be sure to check back in the near future for more Pokemon GO strategy guides, news, and updates. Until then, good luck out there, trainers!
Pokemon GO is available now in select regions on Android and iOS devices.
Source: Pokemon GO Hub