Great premise. A career hit man, working for The Firm, is getting burned out. The same way as some mid-level bureaucrat gets burned out, and starts not to care much anymore about his job. His attention is increasingly being diverted by art, or Art, especially Georgian architecture. He wants to retire and be free to do what he wants, go where he pleases, and just enjoy his peace.
Stand in line.
He doesnt suffer enough, and he's not cold enough, or mean enough -- he's just not well developed enough. And I'd had enough.
The story just needed more ... ooomph.