I have not read many of this character but it interests me how he reacts to his role in civil war? He killed more than half thousand peoples and most of them children so there must be some kind of regret.

Doubtful, didn't someone kill him?

He's alive.

He was left battered to a pulp at the end of the Penance: Relentless mini series.  Robbie recited a registered of everyone who had died in Stamford, and for each name he recalled he smacked Nitro with a wrench.  He then stuck the battered remains in the Penance suit, which had all those spikes sticking in him.  So yeah... he's alive.  And as this is Marvel he'll no doubt make a miraculous recovery.  But for the time being... he's pâté.

Nirtro is a remorseless killer, much like Sabretooth. There are no regrets, except maybe that he didn't manage to kill all of the New Warriors.

I hope someone catches him

LOL i miss the Civil War Arc.
 
Maybe Osborn will call upon Nitro lol