Allentown, PA-based electricity company PPL is hell on the world, but at least it's upfront about it.
On PPL's website is a good section on its carbon emissions. Alas, "PPL currently has no formal greenhouse gas emissions reduction plan in place." It blames the lack of coherent regulation.
Read more: http://www.businessinsider.com/the-15-worst-companies-for-the-environment-2009-9?op=1#ixzz3SFUUD6zU