Checks and Counters
Fairy-types: Fairy-types such as Xerneas, Clefable, Klefki, Mega Diancie, and Fairy Arceus are all able to switch into Giratina and threaten it with super effective STAB moves. Giratina is almost always forced out if it cannot phaze them on the switch. Xerneas and Clefable are especially good switch-ins, as they can both run cleric moves that cures all status afflictions that Giratina has inflicted. Mega Diancie is a complete counter to Giratina, as it has Magic Bounce to completely stop Giratina's moveset as well as being immune to Dragon Tail.
Dark-types: Dark-types such as Darkrai, Yveltal, and Dark Arceus can switch into Giratina and deal huge damage to it with their STAB attacks. Giratina can burn them on the switch, but it is forced out afterwards. Refresh Dark Arceus can switch in repeatedly and pose a serious threat.
Dragon-types: Dragon-types such as Latios, Latias, and Zekrom pose a huge threat if they can get a free switch into Giratina, but this can prove to be risky. Dragon Tail does decent damage to both Latios and Latias, and Zekrom takes a huge risk by switching in, as it can be burned as it comes in. Rayquaza and Mega Salamence are not as threatening, as Dragon-type STAB moves from either of them are fairly rare. Giratina-O is also a threat, as Shadow Force can 2HKO Giratina. Dragon Arceus can also 2HKO Giratina with Judgment.
Ghost Arceus: Ghost Arceus is one of the five Arceus formes that pose a significant threat to Giratina. The Swords Dance set is one of the few physical attackers that Giratina cannot handle, while the Calm Mind set can 2HKO Giratina with Judgment.
Ice-types: Ice-types such as Kyurem-W and Ice Arceus pose a large threat to Giratina. Kyurem-W can outright OHKO Giratina with either Draco Meteor or Ice Beam, while Ice Arceus will 2HKO with Judgment.
