Common answers are:
“BP and Shell”
All could be true but the elephant in the room is that the laws are not good enough. I’ve attached a picture that shows what oil companies own what. As you will see BP and Shell are well down the list. The companies are split by those with shareholders and those who are private/state owned.
The state and private ones emit more pollution per barrel of oil and have a lot more issues like human rights and international law violations but receive far less criticism.
Why do we not assign even equal blame to them as people like BP and Shell? They are far worse but people don’t complain about companies like NICO.
Why? Many reasons but likely the fact that the governments in these countries own all/a big stake in them and thus their fortunes are tied together. They are not going to invest and then implement a law that will limit the company they own. In addition, not all countries have societies where you can speak out and oppose the state. Sometimes the state also owns the media thus you have no chance.
Legally this is not corruption (though there is surely corruption too). People in government with stock is always a bit dodgy. In the UK Jacob Reese-Mogg MP founded an investment group, interestingly the company showed a marked upturn in 2016 when his government came to power.
He has since got out (sort of) as he is now leader of the house but was previously warned for debating in business issues without declaring he had a vested interest in the result.
Sadly you can level this same claim at many MPs.
Ultimately if a country’s leadership is benefitting from an industry they won’t penalise or legislate against them. Also, no one will impose rules on the leadership benefitting in this way as the ones who would do that are the leadership, and thus we are caught in a loop of what you can only describe as “legal corruption”.
Even in Scotland we have a fairly independent environmental regulator that still lacks real prosecution powers (it has some). Bearing in mind we are one of the best it shows what a long way to go there is to get good environmental laws.