Attacking a character with high Athletics (or anything else) is pretty simple, as long as you don't simply try to beat it head-on. Simply put: use maneuvers that aren't opposed by Athletics. (Or, ideally, at all.) FATE is highly flexible, and gives you lots of room to work.
There are lots of ways to turn scores in other skills into aspects. Some simple examples:
Alertness: Create scene aspects! Often! See details below.
Craftsmanship: Break the scenery. Improvise weapons from nearby objects. If given time and a distraction, drop the ceiling on him...
Deceit: Distraction and misdirection. Get him somewhere poorly-lit, and then con him into wasting actions attacking looming sacks and crates, while you plan team ambushes.
Intimidation: Use it, maneuver with it, attack with it. See details below.
Might: Can't grapple the opponent? Rearrange the furniture. Overturn crates or bins to create scene aspects, then jump on them for a height advantage. Shove things into (or onto) your opponent. Or just in his way.
Stealth: Get someone to distract him, and hide. Then set up an ambush. Maneuver to give him aspects like "Blissfully unaware" or "He's Behind You!", then tag them for attacks. Athletics is no defence.
If it's "time to fight" the ghoul, why are you letting him pick the battleground? If he's doing something right now that you need to stop, then sure, you'll have to act now. If not... why fight now? Back off, use assessment to create advantages for later use, lure him into a trap, set up all the tags you can in advance.
This is why it's hard to use Investigation/Empathy in combat... you shouldn't need to. A good investigative character should have figured out what he's up against in advance, and used Investigation for assessment rolls (YS p115, p195).
Against a 'typical' ghoul straight out the book, for example... assess his Insatiable Appetite in advance. Then work out distractions involving fresh meat, or taunt him with how hungry he must be getting. Tag it for effect and say he's already hungry and hasn't hunted tonight... if he fails a Discipline roll, and he'll be in trouble.
Just because the guns are out doesn't mean the social rules turn off. Dresden uses, and falls for, social attacks in fight scenes all the time. This is what Intimidation is for.
Example: Defend one character well. Use scene aspects, get him into cover. Then use those weaknesses you assessed in advance... use Provocation to taunt him into attacking, then sit there taking total defence actions. Total defence + "In cover behind the dumpster" aspect is +4 defence, keeping that character safe... while everyone else coordinates on one big attack.
Or just make Threats attacks with Intimidation, for direct social/mental damage. Maybe you can't hit him... but does he know that yet? He can't defend that with Athletics! If you can't take him out with it, even one good hit can hand out a consequence like "Rattled"... which you can then start tagging to aid your physical attacks.
If you tag personality traits that make you want to kill the ghoul, or that are particularly relevant to how you fight, that's a +2 bonus that can't be counter-maneuvered away. Of course, it gets expensive in fate points fast, but that's why you have them.
Use Scholarship or Alertness rolls, Investigation assessments, or relevant aspects, to explain just why you'd happen to have a bottle of holy water with you.
Check the assistance rules (YS p208). Don't all try to hit the ghoul independently... give assistance to your best fighter. Assistance rolls are against a difficulty 1 or 2 points lower (as GM, I'd definitely rule -2 in a situation like this), and every roll made at the lower difficulty is a +2 bonus all invoked at once for the lead. (Adam gets to make his Fists roll... at +4 for "Bea's got my back" and "Charles is keeping him distracted.")
If you couldn't leverage Alertness into combat maneuvers, you were trying the wrong thing. Use it to create scene aspects. Then tag them for help with maneuvers. Check the declaration rules (YS p116); using Alertness to create an against an overwhelming opponent is the default example!
Declare convenient objects to dodge behind. Add laundry that you can drop over the ghoul's head. Confuse it with a sudden turn into a blind alley it hadn't noticed. Then tag all of them for every bonus you can load on.
That's if you couldn't choose the fight location. If you could... you can do much better. Prepare traps. Level the playing field. (Heck, cover the floor in sticky putty. That should be good to restrict everyone's athletics to +2 or +3 max... which'll bother him a lot more than you.)