Strange could definitely slip up and lose, but he's definitely capable of winning, and I'd say he would win 6/10. He's more than able to have defenses up for almost anything the JLA would throw at him. Then through a combination of dimensional rifts, teleports, bands of cytorrak (the ones that bind people), and regular old magical force, he could have the JLA on their knees.
He'd need some basic info on the JLA members, or MM or Flash would probably catch him off guard, but I was assuming that info came with the prep. The one thing the regular JLA lacks is a good magic-user, and Strange could easily exploit that weakness.
-DM
One week? Easy.
Hour one: Open gateway's to a bunch of nasty demon realms and royally screw up the weather all over DC earth, then retreat to a cold dark asteroid somewhere out in deep space.
Rest of the Week: While everyone's fighting demon armies and saving disaster victims, cast the Seven Gates of Destruction ending DCU, then go home.
Would it be that simple? Probably not. But it could be...
lol
Flash is awesomely powerful.
Green Lantern is awesomely powerful.
Wonder Woman is 90% of Supes.
MM can't be touched, has superspeed and flight and can wreck your brain as soon as look at you.
I wouldn't call them garbage lol. 😄
But with Prep? If JLA don't know what's gonna happen then I can't see them escaping one of his plans.
Except for maybe Flash? He could tag Strange before Strange has even begun to think. Unless he casts an anti-speedforce spell over the area.... but I dunno if he could do that....
Any being with as much power as Strange vs. any group of super powered heroes is going to win most of the battles. It would be no different if it was strange vs. the avengers, titans, xmen. They all loose. same as if it were Dr. Fate. Magical users of such great power with prep and sneak attacks are to be feared.