Azumarill breaks the game. It's pretty great in competitive, but even moreso ingame.
Let's do a headcount, shall we?
- Bulky for in-game standards
- Has over 200 attack by around level 40-something, MORE than enough to OHKO everything in the point in the game.
- On top of that, think an NPC could simply overlevel you? How about, suck on fast leveling rate.
- Learns Rollout. RIP Bug Gym, you can get one just before it.
- Team Flare likes Fire types and Dark types. Okay, so you wall both of those types, and all you have to worry about is the occasionally Golba-- Nope. That's a lie. You're way higher level than them, you're faster even if you're one of the weird people (like me) who EV trains for in-game.
- Alright, so the gyms. Viola gets killed by the low-level learned Rollout, Grant gets simply walled to death, walls Korrina's Fighting types, can simply overpower Valerie, can overpower Olympia, and can wall Wulfric. The only thing you have to worry about is Ramos and Clemont, but hey, you're given a Steelix via trade, so...
- Trainers are a breeze for anything, even moreso with Azumarill.
- Wild Pokemon shouldn't even be mentioned.
- Turns Diantha into a joke. Wait, she was already a joke. Now she might just be a stand-up comedian. The only thing threatening is her Tyrantrum assuming you aren't horribly overleveled and just flat out outspeed it, and maybe her Hawlucha, which Azumarill can easily take a Poison Jab from. And then it just walls her entire team. Assuming you don't take any damage from Hawlucha because usually it just goes for SD or you lead with something smarter, you can just tank Gardy's Thunderbolt and just win.
Tl;dr Azumarill turns X and Y into a joke assuming the one you catch has Huge Power