>>23223824The games rarely profess to suggest that there is only a single one of a legend.
There seems to be only 1 Arceus, 1 Mewtwo (so Red and Ethan never caught it)
The PWT has Sabrina use Mewtwo. That game is happening alongside X/Y, so its possibly she caught it. Its possible there was multiple Mewtwo, as the anime suggests. Or its possible Sabrina having Mewtwo isnt canon, as its just DLC for a battle facility.
There seems to be 1 set of Hoenn legends, as they migrate to Johto in HG/SS, meaning May/Brendan defeated the legends, and released rayquayquay after defeating Deoxys.
There are probably multiple Darkrai... Multiple Golems is pretty much confirmed, including Regigigas. Seems to be 3 of those.
Theres only 1 of the gen 5 legends though, those were unique. Gen 6 too I think.