I know the basics and all that: If the person is X/Y check for Blue Pentagon, check with time amount spent "breeding" and "EV training" if they are, PokeBank etc. But is there any good reliable way to check a Pokemon not PokeGenned/Action Replayed? I want to know to make sure the Poekmons I am buying from this place isn't hacked. Thanks!
There are many things to check to know if a Pokémon is hacked:
1- EV/IVs. The maximal amount of EV a Pokémon can have as of Gen 6 is 508. 510 is still allowed if the Pokémon was imported from Gen 5 as far as I recall, but any higher value = hacked
2- I will always check Shiny Pokémons for hack, because, as you know, it's easy to generate hacked Pokémons and inject them into one's save nowadays (unless if the "hacker"'s 3DS is running the 9.5.0-23+ FW)
3- Check for attacks that Pokémon can't learn.
4- If you're buying an event, use Serebii.net's Event Database and compare everything. Ask the seller if they could leave the Pokémon in an intact state (same moves, same level, and same item), so, you'll be able to easily tell if the Pokémon was hacked or not.
5- Beware of Shiny 3+IV Pokémons. Technically, chances are really low of getting one, so, even if you can get a legal one, stay alert.
That's all for now.