The Avengers barely survived this encounter. They could eventually heal from this but they would never be the same, with a few of them possibly never able to return to battle, to costumes. 

For example Clint Barton lost eighty percent of his hearing while also sustaining burns on  his arms. Wanda Maxmioff had been driven away, pushed to the brink of madness and loss .   Tony Stark was injured so badly no one was sure if he would live or die at any moment. Life support for the foreseeable future. 

The forces, their allies suffered less but still agonizing  fates. The cause of it all...The one who hurt your friends, your family, your heroes wad right there in front of you.

Peter was sobbing into his ash and blood covered hands. The boy was guilty, so vulnerable in that moment. 

 It would have been easy to end the threat as Ross put it.