Holden Karnofsky — Notable For: Co-founder of GiveWell and Open Philanthropy; influential figure in effective altruism; author of 'Most Important Century' blog series on transformative AI

NoteThe source confirms two of the three components: (1) Co-founder of GiveWell and Open Philanthropy — explicitly stated in the infobox and biography; (2) Influential figure in effective altruism — confirmed by the statement 'Karnofsky identifies with the ideas of effective altruism and has both represented and engaged with the effective altruist community' and his listing as a key figure in the effective altruism Wikipedia category. However, (3) the 'Most Important Century' blog series on transformative AI is not mentioned in the source text provided. The source does reference his blog 'Cold Takes' in the External links section and mentions his work on AI safety and AI strategy, but does not specifically name or describe a 'Most Important Century' series. This makes the claim partially confirmed but incomplete.