Xerneas and Kyogre (to a smaller threat) are very threatening, and are the key thing a team has to keep in building, so it is important to know.
The common threats to Xerneas are:
Ditto- It can copy and impostor it, but the problem is Substitute is becoming popular on Xerneas and it needs to be weakened to get properly revenge killed by Ditto.
Dusk Mane: The problem is, you can't have more than one Dusk Mane in a team, despite no Species Clause, it is cartridge limitation, and AG is obtainable, not BH. Dusk Mane needs to be invest completely either in Defense or Special Defense due to it needs to check both Geomancy Xerneas and Zacian-C, so the problem lies with this. The poor function of Dynamax has made Xerneas destructive, and after a Geomancy boost, with Dynamax, it can avoid Defensive Dusk Mane KO from Sunsteel Strike while always 2OHKOing with Max Lightning. Even if it Dynamaxes, it comes to under 10% HP after which Sword Dog revenge kills it.
Keeping all these in mind, how much is a wall Shedinja to Xerneas and some extent Kyogre?