Like I said before, Thanos just easily wasted Thor, Loki, Hulk, Heimdall, and the whole rest of their crew back when he only had the use of one stone, and we don't know if he even had to use it.
Yet Doctor Strange using no stone was able to hold his own with Thanos for some time when Thanos was using multiple stones.
The same Doctor Strange who had gotten his ass kicked by one of Thanos's lackies earlier in the movie.
Talk about Captain America having a bruise....he should be flat with his guts dripping out. Hell, why wasn't Ironman killed by one of those impacts LONG before the "fatal" blow? He's just a regular human. That goes for a lot of them - with all the power that Thanos is wielding, even the NORMAL Thanos, the one who can kick Hulk's ass by himself, should have be killing those mere mortals.
Oh, on a side note - if those portals that Dr. Strange makes can cut off arms, then why didn't he just cut off Thanos's arm when Thanos was incapacitated? Just make a portal over his arm, close it, snip off the arm like what happened to Thanos's lackey.