The following are some examples from a Google document containing a list of 200 of the worse environmental acts from companies.
https://docs.google.com/spreadsheets/d/1an9qOSE2uG4XuzeA4ltUVadDawheTWdJGKRpU5ayCJk/pubhtml
Coal India
57.722
Operated 218 coal mines without 'environmental clearance'.
Largest coal producing company in the world. Owns 80% of India's reserves but production has plateaued owing to poor infrastructure. Tried to privatize 10% through IPO but not many buyers. Sits on billions of dollars of cash reserves and buys mines overseas
Shenhua
31.523
Caused water sortage in inner mongolia, water levels dropped 300 feet and dried up most shallow wells.
http://seattletimes.com/html/specialreportspages/2023525450_chinaserieswaterxml.html
PetroChina
8.577
Killed +200 people in an explosion and poisoned drinking water of over 3 million.
http://www.bloomberg.com/apps/news?pid=newsarchive&sid=apa4SXH_EC6o&refer=top_world_news
Adani Enterprises
25.383
Holds the largest port in India. Good pals with Narendra Modi who is the leading contender for the Prime Minister's post, has awful enviro track record.
http://www.greenpeace.org/australia/Global/australia/volunteer/Adani's%20record.pdf
ExxonMobil
8.181
Worlds largest oil company, spilled 11 million gallons of oil off the coast of Alaska. Partnered with Rosneft to drill in Russian Arctic
http://www.cnn.com/2014/03/23/opinion/holleman-exxon-valdez-anniversary/
BHP Billiton
13.469
Diversified mining and petroleum company with oil, coal and gas operations in Australia and overseas. Responsible for epic environmental disaster at Ok Tedi mine in Papua New Guinea.
https://www.wsws.org/en/articles/2002/04/png-a09.html
BP
6.4
Responsible for largest enviro disaster in US history, the Deepwater Horizon Oil Spill.
Chevron
4.137
Responsible for polluting Ecuadorian Rain forest, refuses to pay settlement.
AGL Energy
2.704
Australian extraction company, currently criticized for attempting to drill under suburban homes.
http://www.abc.net.au/news/2013-02-08/agl-suspends-csg-drilling-under-sydney-suburbs/4508200
Idemitsu Kosan
1.53
Moving forward with controversial Australian mining project in a national park.
http://www.miningaustralia.com.au/news/idemitsu-coal-trucks-halted-by-protestors