The arms industry comes in a close second, but I still stand by my ranking. Not only has the tobacco industry knowingly killed tens if not hundreds of millions in both peace and wartime, not only does it affect non-users of its product, not only have they constantly lied about their product, but they set the denialist and FUD template for every other toxic industry and political movement since the 1940s: fossil fuel extractors, firearms manufacturers, and American conservatives and (as @Kimmo noted) their lobbyists all continue to use the same scummy tactics pioneered by Edward Bernays on behalf of the cancer-stick industry, and we still suffer for it.
The military-industrial complex and (per @Sven_Aitnenton) pimps are refreshingly honest about their evil-doing in comparison.
