Strange, without the Eye of Agamotto and The Cloak Of Levitation was barely able to counter magic assaults from Loki during the Reign saga.
In the assault at New Asgard, Captain America, Thing, Hulk, Wolverine, Vision, attacked the royal palace in an attempt to kill Thor.
Balder helped Wolverine, Strange and Cap to enter in the palace.Then asked them what they want to do.Strange sayed they want to take him down, but Balder answered that the Odin Force is too much for them.
Then they talked about Quicksilver and Warbird freeing Scarlet and her daughter, then Loki teleported in the palace, floating in mid air with WB and QS magically lifted from him.He sayed they must know it's impossible to hide a betrayment to the Eye Of Agamotto, also Strange should know it.
Cap sayed to divide, he can't stop all of them, Loki answered no one can beat him, not if his power is ampified from the eye, he blasted Wolverine, blocked a magical bolt from Strange, meanwhile Cap and Logan fought the royal guards, and Strange teleported Hulk, Thing and Vision in the palace.Loki sayed again they will not stop him and they will not overthrow Thor, and then killed Vision, Warbird and Quicksilver with a magical bolt.Cap sayed he'll stop Loki and the guards, saying to the others to reach Thor.Loki barely stopped Hulk charging him, Balder told to Hogun and Fandral to don't help him, this isn't what Odin want to happen.
Meanwhile Wolvie reached Thor in the nursery where he and Amore were playing with their son Magni.Wolverine sliced Thor's left eye and arm, Thor punched him and disintegrated both his adamantium skeleton and his flesh using Odin Force, but Strange used his lack of attention to put on his neck a medallion.Thor sayed they are crazy, they can't hope to prevail, the Odin Force make him superior to all of them, Strange answered the Odin Force is no more yours.
Thor screamed it's impossible, no mortal can block the Odin Force, indeed no, sayed the Doc, but the Council Of Terrestrial Pantheons can.
Now, this was a Strange without his artifacts and with an object obtained from other gods, but I think that without summoning a powerful entity he can't beat King Thor.
Wow, Loki had the eye.....his powers would be amplified 10 fold or so with it...
Sounds like a story i need to pick up, this all happend while i was out of comics.
But, without invoking a powerful entity, Strange basically has very little power. That's basically the meat of what he does, leeches off of powerful Gods.