I think I have an idea for an answer:
Our first character is:
Nick Fury (from Marvel Comics)
First I had a pretty good vision
But then they locked me up
And blinded me
Two serious injuries Fiori suffered have changed the course of his life: the explosion of a grenade that gradually blinded Fiori's left eye on which he is wearing a patch, and a mine accident that reinforced the infinity formula.
But I kept my heads on my shoulders
Even though they drugged me...
In World War II, von Strucker(Serves as one of the leaders of the Hydra terror organization-In Greek mythology, the hydra was a multi-headed reptile-like water creature) called Fiori for a duel on the island of Norsehaven, and the latter broke commands and met him on the island to satisfy his lust. Before the fight, Von Strocker had offered Fiori a toast, secretly marking his glass. When the two fought the swords, Fury was a stubborn opponent. Finally, Fiori succumbed to the effects of the drug. Von Stroker took care to photograph the event and sent the documentation to Germany for propaganda purposes and to destroy Fiori's reputation
Then I played the role of my life (and death)
And came back both weak and strong
With visions of my past selves
In the film "Captain America: Winter Soldier," Fiori forged his death with drugs and tetrodotoxin. Later, there are ups and downs in which he discovers that not everyone he trusted is reliable.
The second character:
Wolverine (He fought alongside Fiori who was his friend)
As for me, I didn't like school
I got in trouble with the Law
Around 1921, Wolverine decides to emigrate to Mexico, where he was imprisoned in the wake of his power and accused of stealing horses, but continues to engage in criminal activities.
And was torn to pieces
I got blood on my... hands
Really, I killed hundreds !
Wolverine has three removable bone claws in each hand, which means that if someone killed the blood of the person who was killed was physically on his hands,Indeed, he killed a lot.
A victim in two different centuries
In Wolverine, Wolverine is shown at the age of 7 in 1845, according to the film he was born in 1838 (fifty years earlier than his birth in comics), and this is two centuries ago.
And a harbinger of Chaos
Now I survive, glimpsing on my past mistakes
He died as a result of the cover and hardening of the adamantium on his body, but in the new "Marvell Heritage" booklet of September 2017, Wolverine mysteriously resurrected as his healing power recovers, and he escapes from the adamantium cage that has wrapped him in two.
I hope that I have intended the answer you wanted, and in any case it is a beautiful puzzle, congratulations.