Pokémon GO: Every Pokémon You Can't Trade (& Why)

screenrant.com:

A well-known feature of, and any other game, is the fun of trading with friends. This can be one of the best ways to engage with friends and family members, or even meet new people while enjoying a shared hobby. Whether at community events, discussing on social media, or just happening upon another trainer out in the world, being able to share a Pokémon with someone can help form a connection. Some Pokémon can only be found in certain locations, so trading with friends who have traveled to other areas can also help complete a Pokédex.

One of the best reasons for trading in is that a traded Pokémon has a chance of becoming a Lucky Trade, and the older the Pokémon is, the better the odds are of it being Lucky. These Lucky Pokémon are only achieved through a rare chance during trading, but have higher IVs and cost less to power up. The rules operating behind the scenes regarding trades can get a bit confusing, however. Attempting to trade a Pokémon more than once, or trading certain types of Pokémon can cause some frustrations for trainers.

In order to trade with another person in, both players need to be within 100 m of each other, be above level 10, and have enough Stardust.

To prevent players from simply trading a Pokémon back and forth until it either has perfect stats or becomes a Lucky Trade, or both, does not allow trainers to trade any Pokémon that has already been traded, even if it is to a different player. This, sadly, can mean that if someone accidentally trades away a beloved buddy, they cannot get it back as the trade cannot be undone or reversed.

There are many cases where it would be a nice feature to be able to re-trade. Players could then lend a powerful Pokémon to a friend for a battle or to stock up on rare or Shiny Pokémon to then go share with other friends. However, it also does make sense for such a restriction to be in play to prevent unfair advantages of players perfecting their entire Pokédex by infinite trades until every creature is a