Top contributors to climate change are the companies, sources, and countries on Earth causing climate change through greenhouse gas emissions, which are mainly: Carbon dioxide, Methane, Nitrous oxide and the fluorinated gases bromofluorocarbon, chlorofluorocarbon, hydrochlorofluorocarbon, hydrofluorocarbon, nitrogen trifluoride,  perfluorocarbons and sulfur hexafluorideThe extraction and subsequent use of fossil fuels coal, oil and natural gas, as a fuel source, is the largest contributor to global warming.

Carbon dioxide
Ranked 10 most countries
In million tonnes CO2e, China is the largest emitter with 12705; USA is second with 6001, India 3394, EU (which is 27 countries) 3383, Russia 2476, Japan 1166, Brazil 1057, Indonesia 1002, Iran 893, and Canada 736.

Scope 1+3 emissions, cumulative of the years 1988 - 2015, from oil and gas extraction
This heading uses data from  a climate accountability report of Heede, van Der Vlugt and Griffin of the Carbon Disclosure Project. While data of emissions "Direct operational" and indirectly caused from the companies surveyed were indicated by the CDP, requests for data which were ignored by companies and emissions resulting from the use of products originating with companies were included as estimates by the researchers. The data used by the CDP scientists is a composite of quantities of emissions as described via the GHG Protocol Corporate Standard (GHGPCS): Scope 1 and Scope 3 emissions (not including Scope 2) - these three being all the possible emission types. 1 is direct emissions sources from a companies owned or possessed resources, 3 is indirect sources consequential of the production - divided by GHGPCS into upstream and downstream, and 15 categories. Scope 3 emissions are thought to be approximately 90% of the total from any company  and result from the combustion of coal, and, or,  oil, and, or, gas during the conversion of these into energy i.e. as fuel; which is categorized as a downstream. The relevant tables below have a ranking of 20 industrial greenhouse gas emitters from 1988 to 2015 from the Carbon Majors Database (CDP)  report, a July 10, 2017  dataset of GtCO2e.The table below shows the total combined (cumulative) emissions as a percentage of all emissions. Oil and gas production data was obtained from annual reports from company websites and the SEC (2016). For some state owned enterprises, data was sourced from the ‘Oil & Gas Journal’ (1986-2016) 
or is estimated from national statistics (EIA 2017, BP 2016, and OPEC 2016):

All cause 1+3 cumulative emissions
The Guardian newspaper (England, Britain)   and Acciona (bracketed); both citing CDP:

Scope 3
Scope 3 emissions are thought to be approximately 90% of the total from any company (Scope 1) and result from fuel combustion.

Vehicle emissions
Pickup trucks were found to produce the most emissions in a group of vehicles including SUVs and cars, in a survey reported January 2022. Excluding pickup trucks, the most polluting car type surveyed 2017 is the 2011 - 2020 Jeep Grand Cherokee which creates 372 grams per kilometre from the exhaust pipe, the 2007 - 2014 Audi R8 creates 346, thirdly the Chevrolet Camaro 335, the tenth most polluting, the Porsche Macan creates 291.

Home: cooking fuels and technologies
The World Health Organization considers that during 2018 approximately 3 billion people, which was more than 40% of the 2018 estimated global population, used polluting fuel sources in their residences.

Largest sources Carbon Dioxide (Scope 1)
This part details most CO2 emissions for the year 2021 using Climate TRACE:

Largest point source (Scope 1)
This section details production sites at single locations where the most pollution exists or existed in the recent past.
During March 2020, Secunda CTL, owned by Sasol, a synthetic fuel and chemicals from coal  plant in Secunda, South Africa, was the producer of the single most emissions, at 56.5 million tonnes of CO2 a year. The Department of Forestry, Fisheries, and the Environment (DFFE) of the Government of South Africa determined Sasol has until 1 April 2025 to comply with the legal limits for emissions, as described by the Air Quality Act 2004:Part 3; 12; Category 3. Sasol's pledge to reduce it's emissions from the plant by 10% by 2030 was reported during November 2020,  during 2023 it was reported that this was amended to 30%.As of 2021 the gas-fired power plant which emits the most is the Taichung Power Station in Taiwan, with 34.19 million tonnes CO2.

Methane
Sources of anthropogenic production are in the majority: 

natural gas, petroleum, and coal mining: the United States produced the most recent emissions from oil and gas sources at least prior to April 2023.
livestock  production systems; manure and enteric fermentation,
waste deposit sites: landfills   waste water

See also
Afşin-Elbistan C power station
Attribution of recent climate change

Further reading
Arkush, David; Braman, Donald (23 January 2023). "Climate Homicide: Prosecuting Big Oil For Climate Deaths". Harvard Environmental Law Review. papers.ssrn.com. 48 (1). SSRN 4335779.
Çınar Engineering Consultancy (March 2020). Afşi̇n C Termi̇k Santrali, açık Kömür İşletmesi̇ Ve Düzenli̇ Depolama Alanı Projesi̇ Nihai ÇED Raporu [Afşin C power station, open coal workings and regular storage area final environmental impact report] (Report) (in Turkish). Ministry of Environment and Urbanisation (Turkey).
Derwent, Richard G. (9 May 2020) Global Warming Potential (GWP) for Methane: Monte Carlo Analysis of the Uncertainties in Global Tropospheric Model Predictions Atmosphere 2020, 11(5), 486; https://doi.org/10.3390/atmos11050486
"FAQ" (PDF). ghgprotocol.org. Greenhouse Gas Protocol. Retrieved June 16, 2023.
Reay, David S (2007). Greenhouse Gas Sinks. Wallingford, Oxfordshire: CABI. p. xii. ISBN 9781845931896.
Sauvage, Grégoire (18 June 2023). "'Gateway to Hell': Turkmenistan urged to plug gas leaks driving climate change". www.france24.com. France24.
Supran, Geoffrey; Oreskes, Naomi (23 August 2017). "Assessing ExxonMobil's climate change communications (1977–2014)". Environmental Research Letters. IOP Publishing Ltd. 12 (8): 084019. doi:10.1088/1748-9326/aa815f.
"The Causes of Climate Change Human activities are driving the global warming trend observed since the mid-20th century". climate.nasa.gov. NASA.
"World Population Prospects 2022". www.un.org/development/. United Nations.

References
External links
Stephen Conmy Apr 4, 2023 News Analysis The 20 most polluting companies in the world https://www.thecorporategovernanceinstitute.com/
Leakey, Andrew D.B.; Ainsworth, Elizabeth A.; Bernacchi, Carl J.; Rogers, Alistair; Long, Stephen P.; Ort, Donald R. (2009). "Elevated CO2 effects on plant carbon, nitrogen, and water relations: Six important lessons from FACE". Journal of Experimental Botany. Journal of experimental botany, Oxford University Press & University of Illinois Urbana-Champaign. 60 (10): 2859–2876. doi:10.1093/jxb/erp096. PMID 19401412. Retrieved Jun 14, 2023.
Glossary: Well tank wtt emissions, United Nations Economic and Social Commission for Western Asia, https://www.unescwa.org/
C. Wulf, M. Kaltschmitt Environmental impacts of hydrogen use in vehicles 15.2.2 Well-to-wheel analysis, Elsevier, https://www.sciencedirect.com/
Most car Models sold Worldwide 2022, Statista, https://www.statista.com/
Kennedy, Charles (16 Sep 2021). "Home Latest Energy News". oilprice.com.