Ask HN: Cofounder Equity Battle

I vested 16% at a startup with a fair market valuation of around 1 million. The cofounder and I were conflicting for months, so we decide I transition out. I initiate the exit. The cofounder resists, but finally agrees. After my fully cooperative cofounder transition, he issues me a termination notice for cause, citing not meeting company expectations (citing his complaints about me during our conflicts), invoking his board right to reclaim all of my vested equity. But he said he wanted to be generous and only take back 97%. Worst betrayal of my career. He can do this in contract, but it can definitely be challenged. Further, he is holding 6 months of salary on me as leverage for me to sign away this equity. I was open to giving back equity, but he went about this in the worst way possible. Not even a single ask. Just immediate legal threat, board leverage, salary coercion. I politely declined his first offer. I talked to a good firm (Grellas Shah). I have a good case. How much it’s worth fighting? Debatable. The grounds are utter BS. In our last company meeting he said I was the best in San Francisco. I’m already onto a better venture, but still, not sure if I’m going to let this one slide. He’s actually on the hook for a long list of civil and criminal penalties. Thoughts on gameplan?