Were there any basic NPC trainers that gave you some trouble?

[IncineROAR]

In ORAS, I don't remember what route, but it's near the Safari Zone. There was this stupid trainer that should have been really easy, but his stupid Magnemite with Thunder Wave and Supersonic gave me a run for my money. The Magnemite isn't what caused my Pokemon to faint, it was the fact my Pokemon was too stupid to overcome the confusion.

 

[Harryghost]

I don't remember the exact details, but there was this one guy in Platinum who gave me SO MUCH trouble with his Tangrowth... Argh! It was so hard to beat, I actually had to go out of my way to catch a Ponyta to take it down.

 

[Dieter]

Cooltrainer Jennifer and her Milotic on Hoenn route 120 is one I always dread and look forward to. It's properly challenging, especially after having had a couple of battle before already, though recover can get pretty annoying. Can't remember how I beat her on my last play-through though. The aforementioned Ace Trainer duo with a Gyarados and Raichu is rather troublesome too.

The route west of Pastoria also had an Ace Trainer Duo that sometimes gives me trouble, especially if I was unprepared for the Scientist right before and hadn't healed up in between. Other than that, I can't really think of any difficult NPC trainers, other than the ones that were at the end of a long route

 

[~ Blazing White Yang]

That Battle girl in Reflection Cave, in my first playthrough of X...Her Hawlucha or another Pokemon had Rock Tomb and caught me off guard...Knocking out my Braixen and Flying Pokemon, which I was training for the Gym :s

 

[IncineROAR]

Guzma's Pinsir with Stone Edge caught me off guard the other day. It's been a while since I played Ultra Sun / Ultra Moon. Guzma was a pain in the neck, whereas on the other hand I had no issue with Lusamine or Gladion.

 

[Pilup99]

There's an Ace Duo on Johto Route 47, I think... The one with the cliffs. They have an Electabuzz and a Magmar, and I was woefully unprepared for them once. They ended my Nuzlocke in an instant.

 

[Incinerawr]

Leafgreen.

Trainers with Minimize Muks.

Rage all day.

 

[TeaWest]

The token fisherman with 6 Magikarps usually tests my PATIENCE

 

[Nitro Indigo]

Yesterday, I got stalled by a Sealeo belonging to a Swimmer in Alpha Sapphire who knew Hail, Rest, and Swagger. I didn't have any moves super-effective against it because I limited my team for the Mossdeep Gym.