[Scarfwynaut]

The range of a check and a counter is pretty wide in my opinion it can be very hard to pin down exactly what each is. Generally, a counter is a pokemon that can switch in once or more with little to no risk to itself and is capable of taking out the pokemon. A check is something that much switch in either on prediction of a move or after a pokemon is killed. This is a pretty skechy definition take for example the following situations:

1. Chansey into Yanmega: this is about as close as one can get to a true counter, Chansey littlerally fears nothing from yanmega, Chansey isn't worn down slowly, and yanmega can't do anything do it at all. Counters like this are rare.

2. Hippowodon into Lucario: Hippowdon can take anything (outside of high jump kick) Lucario has, and without spikes up, there is little chance of a 1HKO, and Hippowdon will just 1HKO Lucario if it attempts. Hippowdon can recovery any damage Lucario tries to put on it easily, meaning one on one, Lucario can't beat it. However, Lucario can bring Hippowdon to very low health with a +2 close combat, making it easy pickings for another sweeper. Hippowdon walls Lucario, but still has some risk. But because Hippowdon can beat Lucario, its still a solid counter.

3. Slowbro into Terrakion: Slowbro can switch into Terrakion and do massive damage to it. Against swords dance, Slowbro is 2HKOed, but still can pose a significant threat to Terrakion with scald or psychic / psycho shock. Its a similar story vs CB terrakion, slowbro can switch in, but still faces the risk of being slowly worn down and beaten. Slowbro can not always beat Terrakion one on one, but can still pose a threat to one or weaken it, generally Slowbro is considered a counter, a bit a shanky one, to Terrakion. (interestingly this draws parallels to the defensive check I mention later)

4. Chansey into Reunicles: basically, there are 2 types of reunicles, trick room, and calm mind. Chansey looses to calm mind, but not to trick room. It comes down to the set of the opposing pokemon here more than a specific move. Chansey is a solid counter for one, but loses to the other. To be honest, I don't known what you would call this.

5. Scizor vs Latios: Scizor can switch into Specs - Latios one time (unless its specially defensive with roost), on the second go it is finished off by pretty much whatever move Latios has. Scizor can in fact pursuit it to death, but if its lets say locked into surf, it can maybe 2HKO Scizor. Then it becomes a mind game, both pokemon can do significant damage to each other and it comes down to prediction who wins. (this is assuming no HP fire lol) The key here is Scizor can in fact switch in and maybe take it out, so this is again is usually considered a counter.

6. Focus sash Alakazam into Keldeo: because of focus sash here, Alakazam can come in pretty much all it wants and threaten to 1HKO with psychic, however, it can literally only do this once, that's it. Because of the fact that this is a one time guaranteed switch in, is it a check or counter? A fine line is probably drawn somewhere around here.

7. Mamoswine into Salamence: Salamence can do massive damage to Mamoswine if it switches in, but, Mamoswine if it predicts a dragon dance, and effectively come in, or after something has died, and threaten Salamence in return. This is probably as close to a true check as one can get.

8. Amoonguss into Thundurus-T: In this situation Amoonguss (if the spore if already fired off) will lose to Thundurus-T, but Amoonguss still takes a huge chunk out a Thundurus-S health, allowing something else to finish it off. This is what I consider a defensive check, other examples include defensive Politoed taking a hit a firing off a scald, or Forretress killing a dragon locking into outrage, they can finish or weaken a theat, but may lose to it.

What do you guys think? Where is the line? Pick apart my examples I am curious on how the community feels about each one.