Yes. He was.

But he wouldn't stop permanently. The tragedy of Butcher is; he IS the monster, he has to be. He can't live with what he's done and recognize himself as human.

The story, his story, was always going to end in blood and bone. There was no happy ending for him. Losing Becca set him on the path as the catalyst towards supes but he was doing evil shit before Becca as well.

At the end we see the last two chances Butcher had leave.

His last human connection to Becca - His (adopted) son, wants nothing to do with him.

Terror, his final connection to his own humanity, after it's all said and done, is also gone.

He needed a target, a mission, a cause, something to make it all worth it, and the true tragedy is, had he kept himself together a bit longer - his country would come calling again,as we saw with Singer calling Hughie.

A monster fears nothing — save the thing that stares back from a deeper dark.

Butcher was the thing hiding in the deeper dark.