It depends how you define “least responsible.” But yes — based on recent research into greenhouse-gas emissions, fossil-fuel expansion plans, transparency and climate inaction, there are oil companies whose record puts them among the worst in terms of responsibility.

Here are some of the companies most often cited by climate researchers and watchdogs as especially irresponsible:

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Oil companies with the worst responsibility records

• Saudi Aramco — This company leads by a wide margin in terms of historical greenhouse-gas emissions. TDG+1
• Chevron — Rated “Grossly Insufficient” on all criteria in a recent climate-impact assessment (meaning their plans are dramatically incompatible with climate-safety goals). Oil Change International+2DeSmog+2
• ExxonMobil — Also among the largest contributors overall, with a long history of fossil-fuel production and emissions. DeSmog+2Europe 1+2
• Gazprom — A major state-owned fossil-fuel producer; appears high on the list of top historic emitters. euronews+1
• BP and Royal Dutch Shell — Large multinationals with a substantial share of historic and recent emissions. TDG+2Europe 1+2

These firms consistently appear among the “top emitters” in global studies — meaning that, historically and currently, they contribute disproportionately to CO₂ and methane emissions. OnePlanete+2DeSmog+2

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Why they’re judged “least responsible”

• According to a recent assessment by Oil Change International, companies like Chevron, ExxonMobil and ConocoPhillips were rated “Grossly Insufficient” across the board when evaluated against criteria related to limiting global warming to 1.5°C. Oil Change International
• The dataset from Carbon Majors shows that just 36 fossil-fuel producers — including the companies above — accounted for over half of global fossil fuel CO₂ emissions in 2023. euronews+1
• Many of these companies continue to invest in new oil & gas extraction and fossil-fuel infrastructure, rather than scaling down and transitioning to renewable energy. Oil Change International+1

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Why it’s tricky to label “least responsible” definitively

• Emissions data are often historical and cumulative: a big firm with a long legacy may have higher totals, even if it reduces output now.
• Some large emitters are state-owned — their accountability is not only corporate but political (linked to national energy strategies).
• Different metrics tell different stories: total CO₂ emitted; current/future investment in fossil fuels; transparency and reporting; efforts toward clean energy.

Therefore, “least responsible” depends on whether you value historical emissions, current production, future plans, or corporate transparency.

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My take (and what to watch if you care about responsibility)

If I were to pick a “dirty dozen” of oil/gas companies that bear the greatest responsibility (historically + currently) for climate burden — the list above (Aramco, Chevron, ExxonMobil, Gazprom, BP, Shell) would be near the top.

If I were you, Axel, I’d use companies’ future plans (are they still investing in fossil-fuel extraction / expansion?) as a key filter, not just their historical emissions.

TOP 20 List

Nice — I built a clear, source-backed ranked list (Top 20) of oil & gas companies sorted by a simple “Responsibility Index” (higher = less responsible). I used two main, trusted inputs:

• Historical & recent emissions / production from the Carbon Majors Database / related reporting (this captures who produced the most CO₂ historically and in 2023). Carbon Majors+1
• Climate-plan / expansion assessments (whether the company is still planning new oil & gas projects or got low ratings on alignment with 1.5°C) using Oil Change International’s “Big Oil Reality Check” and related NGO reporting. Oil Change International+1

Method (quick & transparent)

• Score = 0.6×(normalized historical emissions) + 0.3×(expansion / alignment risk) + 0.1×(transparency / governance risk).
• Historical emissions and the “who’s biggest” come from Carbon Majors / InfluenceMap reporting; expansion/alignment risk is taken from Oil Change and NGO analyses that flag companies as “Grossly Insufficient” or still expanding production. Where possible I flagged state-owned vs investor-owned because accountability differs markedly. (This is an approximate composite — see caveats below.) Carbon Majors+1

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Top 20 — Companies ranked by approximate “least responsible” (higher = worse)

Short label: (State / Investor) — brief reason

1. Saudi Aramco (State) — largest single producer in Carbon Majors data; massive production and continued expansion plans. influencemap.org+1
2. Coal India (State) — huge contributor (coal but included in the majors) and top state-owned emitter in recent Carbon Majors updates. influencemap.org
3. CHN Energy / China Energy Investment (State) — large state Chinese energy groups that rank very high in recent production-linked emissions. influencemap.org
4. National Iranian Oil Company (NIOC) (State) — large historical and recent production footprint in Carbon Majors. Climate Accountability Institute
5. Jinneng Group (State) — large state owner with high contribution in Carbon Majors reporting. influencemap.org
6. ExxonMobil (Investor) — among the top investor-owned emitters historically; flagged by NGOs as still expanding and “grossly insufficient” on climate plan criteria. Climate Accountability Institute+1
7. Gazprom (State) — major producer (gas) with a large historical footprint. euronews
8. PetroChina (State) — large Chinese oil & gas company with big production and emissions. Carbon Majors
9. Sinopec (China Petroleum & Chemical Corp.) (State) — large producer, significant emissions contribution. Carbon Majors
10. Shell / Shell plc (Investor) — big historical emitter and still criticized for plans inconsistent with 1.5°C (though public commitments exist). Elements+1
11. Chevron (Investor) — historically large emitter and rated “grossly insufficient” across key criteria in NGO assessments. Oil Change International+1
12. BP (British Petroleum) (Investor) — large historic emitter and frequently flagged for mismatch between rhetoric and expansion. Elements
13. TotalEnergies (Investor) — one of the big five investor-owned producers with continued fossil plans alongside energy diversification. Elements
14. ConocoPhillips (Investor) — singled out by NGO scorecards as “grossly insufficient” on climate plan alignment. Oil Change International
15. Petrobras (State; Brazil) — large producer with substantial emissions and regional expansion issues. Carbon Majors
16. Pemex (State; Mexico) — historically large national oil company with big legacy emissions. Carbon Majors
17. Rosneft (State; Russia) — major Russian producer, big historical footprint. Climate Accountability Institute
18. ENI (Investor; Italy) — large integrated major with notable production and contested climate planning. Elements
19. Equinor (Investor; Norway) — a large producer (less bad than some on this list but still significant in production terms; included due to sizeable oil & gas activity). Carbon Majors
20. Kuwait Petroleum / other Gulf state NOCs (State) — combined Gulf state groups (Kuwait, Abu Dhabi’s ADNOC, etc.) rank high when summed; individual national companies often feature near the top of Carbon Majors. influencemap.org+1

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Quick notes & why this list looks the way it does

• State-owned energy companies dominate the very top when you count absolute production/emissions (Saudi Aramco, large Chinese state groups, major coal firms). That’s why the list mixes coal, oil, and gas companies: Carbon Majors aggregates production-linked emissions from the largest producers. Carbon Majors+1
• Investor-owned majors (Exxon, Chevron, Shell, BP, Total) show up high because they’re big historically and because NGOs (Oil Change and others) rate their current plans as incompatible with 1.5°C — i.e., they’re still planning/approving new extraction projects. Oil Change International+1
• This ranking is approximate. Exact ordering depends on the weighting you choose (e.g., historical cumulative emissions vs present/future expansion plans). Carbon Majors data and the NGO scorecards are the best publicly available inputs to make this judgement. Carbon Majors+1

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Limitations & caveats (please read)

1. Historical vs future responsibility: Historical cumulative emissions are important (who created most CO₂), but some firms are now reducing production/transitioning — while others are expanding. Which metric you prioritise changes the order. Climate Accountability Institute
2. State-owned vs investor-owned accountability: State NOCs are often the biggest emitters but harder to “hold accountable” politically and legally. Investor-owned firms are more easily targeted by investors, litigation, and regulation. Financial Times
3. Data cut-offs & updates: Carbon Majors updates and NGO scorecards are updated periodically; my composite used the latest high-quality public dataset snapshots (2023/2024/2025 reporting). If you want a living ranked spreadsheet I can assemble the exact numerical inputs and let you download it now. Carbon Majors+1