A perfect Giratina CP in Pokémon GO is set around 3,683. There are two forms to Giratina, so let's look at how strong each of them are.
The game calculates CP (combat power) by a Pokémon's IV (individual values) for each stat. You'll know if a Pokémon has max IVs in a stat if the bar is full and red when you take it for appraisal.
Perfect Giratina CP Pokémon GO: Which Form is Better?
Want to test out your Remote Raid Passes? We’re excited to announce that Raid Hour is coming back this week, this time featuring Altered Forme Giratina! Use a Remote Raid Pass to join any raid that you can see on the Nearby screen or tap on the map.
— Pokémon GO (@PokemonGoApp) May 4, 2020
The IVs of a Pokémon can't really be raised, so to find a Pokémon worth investing resources into will be a matter of catching a bunch and appraising them all. If it's for Giratina, it'll be worth examining which one of it's formes is worth acquiring.
Perfect Giratina CP Pokémon GO: Altered Forme
Giratina Altered Forme is when it has legs. It takes this form when it leaves its native Distortion World. As Giratina isn't in its element here, this forme is slightly weaker. Altered Forme has a max CP of 3,379.
Perfect Giratina CP Pokémon GO: Origin Forme
Giratina's true form sees it at peak power. This is the forme Giratina takes when it resides in its home dimension. Giratina-Origin has a max CP of 3,683.
Both Giratinas are quite formidable in competitive, and they actually compete with each other over which is stronger. Origin forme takes the crown due to the CP increase, but it's only a marginal distance. Giratina is one of the strongest Pokémon in the game, so you can't go wrong with either.
