How Much Equity to Give Co-Founder

I started this company about 2.5 years ago and brought someone on as a business co-founder. He contributed significantly to shaping the product, which was developed by me and a small team of 2–3 others. His time commitment varied—minimal at first, but up to 40 hours per week toward the end. The main issue is that, over 2.5 years, he did not approach a single investor, which was a key part of his role. I asked him to step down 45 days before his 1-year cliff (the agreement was 20% over 4 years). Opinions vary—some suggest giving him 5%, others 0.5%. I’m trying to determine a fair amount.