How would you deal with this?

Ok, so I'm probably going to give this enemy another skill now to surprise the player, here it goes anyway

There's a point in my game were one of the mains characters has to fight alone. Anyway, there's one enemy that absorbs HP and debuffs ATK, MAT, and REF (AGI) by two levels with just one skill.

Without buffing or status, how could the character deal with this? I'm trying to make even the most generic battles strategic, and need some advice thanks

Oh, and I'm not saying how the character is already structured, because I don't want that tempering your awnsers or giving spoilers. Except to say she's a physical attacker

Items that have to be used in a certain order to overcome the enemy?

Maybe elemental damage? Without knowing what sort of enemy it is, it's hard to say. But even if the player hasn't learned any spells at this point, maybe they've found a disposable attack item which uses an element the enemy is vulnerable to.

Maybe a potion which gives the user a "poisonous" state: when the enemy tries to drain HP, she is damaged instead.

i was thinking more in terms of skills. skills are, after all, unlimited. If you run out of the item, you would be out of luck in terms of gameplay 

Give this enemy an attack pattern. 1 on 1 battles don't open much room for strategy, at least not as much as battles where you have more party members to help you. Just remember that in a 1 on 1 battle, a player can only take 1 action. It will either be attacking/dealing damage or buffing/healing. If the player cannot outheal the enemy damage, the battle is broken. So if this enemy uses his powerful debuff ability every turn, the player will be in big trouble.

Two things I can think of from the top of my head:

1. Make the enemy use this debuffing ability only on certain turns, e.g. turn 3, 6, 9, etc.

2. Have the player use a skill or item that gives him/her immunity to debuffs for a few turns. This will make it worth their time to spend a whole turn not dealing damage to the enemy, because the payoff is greater (i.e. they get to resist debuffs for several turns).

Hope this helps.

I'm already doing 1. and I want to avoid 2 if i can

Edit: OK, I'll be honest with you all, I've already figured out a way to set up the skills so they can deal with this without having to resort to corny, situational methods, before i even posted this. I'm just looking to see if there are other ways to do this

I would combine the buff with some implicit weakness.  Keep in mind an "Element" can be anything.  You could have "Edged" and "Blunt" attack "Elements"  for a purely physical attacker --- the former using swords, the latter using clubs.

So maybe the enemy is particularly vulnerable to Edged attacks when the buff is in effect.   Or maybe the physical attacker has a Skill that Stuns the enemy.  And the buff makes the enemy particularly vulnerable to Stun (or some other harmful state).

So, yes, the enemy is nearly invulnerable, damage-wise, but certain specialized Skills have a very good chance of Stunning the enemy. Or the Skill does a specialized type of damage that bypasses the debuffs --- maybe a fixed damage Attack which isn't much more than the character's normal Attack...but which is really effective against this enemy, because the enemy relies on the player debuff.

I've also had boss fights where the boss has Counter-attack and Magic Reflection at 100% --- for the first few rounds.  After that, the specialized state drops, and the fight can begin.