An everlasting exchange

A soul for a soul
A price that took a toll
They needed the soul stone
To do this, one should be thrown
Hawkeye and the widow both played a role
The Widow’s life, Red Skull stole
Her efforts are something the avengers extol
This left hawkeye alone
A soul
Its loss was not part of their goal
When he was zapped, Hawkeye lost all control
At this fight scene, their abilities were shown
And this tragic death will be known
But what exactly fell down that hole?
A soul