who is the good/evil man?

I think a better way to look at this is sin and redemption rather than good/evil. The mariner kills the albatross and is fixed with it around his neck,

Ah! wel-a-day! what evil looks

Had I from old and young!

Instead of the cross, the albatross

About my neck was hung.

We all sin. This story is also one of redemption. The mariner goes through his metephysical ordeal to understand the beauty of creation and hence experience redemption or transformation.

O happy living things! No tongue

Their beauty might declare:

A spring of love gushed from my heart,

And I blessed them unaware:

Sure my kind saint took pity on me,

And I blessed them unaware.

The selfsame moment I could pray;

And from my neck so free

The albatross fell off, and sank

Like lead into the sea.

No