How come my Tentacruel has a notably higher Attack stat than Sp. Attack stat?

Question

Sorry if it's a stupid question. Although I've played Pokémon for a long time, and played most of the main line games (except the latest, maybe one day I'll get to afford it), I've never been very involved with how stats work, and IV's and EV's and all that (still don't know what either of those terms mean). I've never played competitive and only played the main story, focusing on higher lvl and Super Effective moves to win fights. I've tried putting more attention to stats now lately, using moves that complement the Pokémon's highest stats when it comes to physical or special moves. Avoiding Pokémon with low stat averages on Pokemondb in favour of ones with better stats. Even trying to match Phycial and Special moves to the opposing Pokémon's weakest defensive stat on average (when type advantage is irrelevant).

In my latest playthrough of Pokémon Sun/Moon. I tried having a character that was more similar to the Team Skull in terms of style and team (like the unlikely Hero type deal). With mostly Dark, Ghost and Poison type Pokémon and stuff. Tentacruel was one Pokémon I added to the team as I lacked any water type for the Fire trial and the Rock grand trial that follows (my starter Rowlet/Dartrix could work in the latter, but the flying typing made it risky). Looking at my newly evolved Tentacool's stats before the grand trial, I saw its attack stat was 10 higher than its Sp. attack, and thus assumed higher attack was normal for Tentacruel, it made sense with all the tentacles and all (especially since its sp. attack was written in blue in the summary screen, while its defense was in red, making me assume the nature gave higher sp. attack and lower defense). So when picking abilities I was aiming for physical attacks, and for Poison Jab. With my current movepool at lvl 31 being:

Nature: Imish
Ability: Clear Body
- Scald
(highest available power Water move so far in the game, for the STAB bonus obviously, and highest possible dmg with water Z-move)
- Venoshock
(for the nice double dmg to poisoned targets)
- Barrier
(since its Sp. df is already high, I though a boost to regular df could make it quite the tank again most opponents)
- Poison Jab
(For a high power Physical poison STAB, and the chance to poison for the x2 dmg on Venoshock)

However, after looking up recommended moves on Tentacruel, to see what other people built on it out of curriosity, I saw pretty much no one else using physical moves on it. This confused me, until I looked it up on Pokemondb and saw on average its Sp. attack was 10 higher than its Attack on average, the exact opposite of mine. So what's the deal? I know those stats are averages, but since its nature doesn't seem to lower its sp. attack, I can't seem to think of a reason why it would be 20 points lower than the average.

Comments

Impish does in fact raise physical defense and lower special attack. Try reading this if you want to learn more about stats. https://bulbapedia.bulbagarden.net/wiki/Statistic

Answer 1

It's because of the EVs you're gaining when you fight with your Tentacool/cruel.

Whenever you defeat a Pokemon in the standard game (as in, not playing against other IRL players), you gain one or more EV (effort value) in a stat. For every four points gained, you gain one bonus stat point to the respective statistic.

Not only do you have Impish, a nature which lowers your special attack (if you look in your summary page, blue is the lowered stat while red is boosted), but you have probably also been defeating Pokemon that return Attack EVs. That is inevitable, as defeating trainers is necessary to complete the game, but still correctable (we'll get to that). The nature you have unfortunately is not recommended for Tentacruel, and cannot be changed in Sun & Moon.

So there's your answer, but I'd be happy to teach you what else you should know.

You can have a maximum of 508 collective EV points on a given Pokemon, spread however you like at a maximum of 252 in any given stat.

IVs (internal values) are ones that your Pokemon is born with and cannot be modified without it being level 100 and having the necessary equipment. They range from 0-31 ("perfect") and ideally necessary stats are all at 31 to be competitively viable, though some may choose not to have all 5-6 and settle for a few necessary ones.

There are many things you can do to boost the process of getting your Pokemon "trained" in this specific sense, but you have the basics now of how the system works. If you have further questions about that at this time, ask another question I'd be happy to teach you. :)