Mighty Strike is extremely vulnerable during its start up. If Thor isn’t mindful of his spacing, if he doesn’t take into account how fast the other character is, if he isn’t protected by an assist, often times you don’t even need to air throw him out of it. You can literally dash under him, and get a full combo before he even lands. X-23 and other speedy characters are especially great at this.
Really if you take advantage of how slow he is, you won’t need to respect much of anything he does. A good Thor will be trying his best to space things out while applying pressure, but if you’re always in his face, he won’t ever get that chance. People see Mighty Strike and think, “oh he turns himself into a flying hit box, I can’t do anything about that” when really you got all the time in the world to do whatever you want about that. Don’t respect give him any respect unless he earns it.
And if you really wanna mess up Thor’s day, use an anti air assist. Thors like to stay in the sky because that’s the only place he doesn’t suck, but he’s really not that good at being dominant there unless you let him be. Strider will knock him out of all of his air actions. Jam Session when used properly will too. Sure, if you use these assists against a Thor baiting them out, they’ll get blown up, but if you use them in response to anything he does, if you use them reactively instead of proactively, you’ll give him a very bad day.
Then of course there’s the keep away zoning that he hates so much. This adds on to controlling the air space that he wants to move around in so much. For him to pressure you, he has to get in. He can’t get in with a bunch of hit boxes on the screen. Mighty strike can break projectiles when its active, but the distance it covers is extremely lackluster for the amount of time it takes to start up, and if he charges it, it takes that much more time.