Worst mistake to ever make in the Pokémon world...

[RioluRiku]

That feel when you see your posts from 3 years ago.
How time flies....


Oh yeah, worst mistakes.

Definitely would have to be choosing Tepig.

Never. Again.

Fairy type Pokemon are coming out with draining kiss so letting them kiss you would probably be a bad idea as well...

[SirBlaziken]

Nice to see you alive again.

Sending out a dratini against a sylveon

[MzLuluZombi]

Asking Arceus, "So, what are you supposed to BE anyway?"

Having a Pokémon battle in a china shop.

Taunting a legendary after you catch it with a Quick Ball.

Find a shiny Pokémon... in the Safari Zone.  _{Curse that Girafarig for favouring its freedom.}

[SirBlaziken]

Using a dratini that only knows dragon type moves against a fairy type.

[vegparcriddle]

Not saving before taking on articuno

[Meowstic Royalty]

Saving next to a Taxi in Lumiose City.

[Captain Jigglypuff]

^I do that ALL the time and nothing happens to me!

[Reluctant Wailord]

Using Blastoise as anything other than a durable utility.

[SirBlaziken]

Going up against the combo of aeguslash and mega blaziken.

Between the 2, ko'ed 5 pokemon on a guy's team.

[quack98]

^that combos pretty easy to beat on it's own Mega Mawile springs to mind, with Sucker punch to KO Aegislash and Fairy STAB to KO Mega Blaziken... Although, an effective partner for it would be something like Giratina in Übers, or Jellicent in OU, to handle Blaziken more reliably.

Anyway, mistakes...

Going to Sinnoh elite 4 with a grass type.

[Meowstic Royalty]

Going to Sinnoh elite 4 with a grass type.

Well I guess I should be worried that I've got a Torterra as a powerhouse and I'm in Victory Road.

[Legacy]

Poking Espurr/Meowstic in the ears would probably be a massive mistake. Oh, and kicking a Voltorb/Electrode.

[Captain Jigglypuff]

Letting Ash and Pikachu "borrow" your bike
Cutting Jessie's hair
Underestimating the abilities of Hawlucha (easily the second best non-Legendary Kalos Pokemon after Sylveon due to the extensive movepool and types of moves it can learn)

[the bread dragon]

asking a woman when their baby is due when they arent really pregnant.
it could be be bad in the pokemon world, too

[SirBlaziken]

Sending out Shedinja when any entry hazards are up. Honestly, some people.