Out of curiosity for the 3/10 times where Strange wins, how do you think it happens?
Actually hurting Thor or banishing him with a portal?
On the other hand he engineered the deaths of Thanos and his army.
I see Strange winning by keeping Thor off balance long enough to:
- trap him in a time loop or de-age him to infant Thor.
- transform Thor's lightning into butterflies, after which Thor storms off in embarrassment
- blind Thor with the cloak of levitation, and then tie his boot laces together.
- banishing him in a part of the multiverse from which he cannot return ( like the mirror dimension or Ibiza)
- transform him into a harmless form.....like a frog ( a nice reference dropped in Ragnarok about the classic storyline).
- open a portal under him and close it when he's part way through.
- send him home crying with his withering sarcasm.
-some other random effect, because Strange's powers are a bit like that ( who knew he had a spell for turning a flood into a waterspout? ) He has a bunch of random effects in his battle with Thanos that are hard to describe ( e.g.turning a black hole into butterflies, making an object burn people if they try to take it off him )
So something like that. What the MCU shows time and time again is that on any given day a stronger character can be beaten by a weaker one - under the right circumstances ( eg Cap vs Iron Man, Valkyrie taking down Thor so easily- because she has a weapon against which he has no defence ).
While Thor should beat Strange handily most of the time - it's possible under some circumstances for Strange to win.
Second, Strange foresaw a possible future which assisted in the resurrection of trillions of beings that Thanos killed - the line of argument you are pursuing is very similar to the one that points out that Luke Skywalker committed mass murder when he destroyed the Death Star. While you have point, I suggest the greater good argument is a strong rebuttal.