A key member of the Black Order of Thanos was missing in Avengers Infinity War, and thankfully!
Except the original 6 Avengers, there aren't really big world who came out alive from Avengers Infinity War . An unexpected end (or almost) which managed to surprise the spectators and tape them to their seats. Despite a completely dire situation, the Captain America and Iron Man team still managed to turn the situation around and save everyone in Avengers Endgame . An achievement that would probably not have been possible if the Black Order of Thanos had been complete. A major member was indeed missing, the super-villain called Supergiant. His powers ? Read, control, and above all devour minds.
In other words, Supergiant would have been able to not only pit the Avengers against each other and make them fight each other, she already did in the comics, but most of all she could have made them lose their intellectual abilities. However, it is thanks to their knowledge that the heroes of MCU managed to bring their friends back to life and stop Thanos. For example, without the genius of Iron Man, how could they have solved the problem of time travel ?