What are the top 3 missed opportunities for individuals who have just experienced a company exit or liquidity event?

Hard to rank three so just consider these pieces of a toolkit. Actually applying the tools depends upon your personal situation/preferences/goals/etc.

1. Donor advised funds (DAFs) are investment accounts, created for the sole purpose of supporting charitable organizations. A donor-advised fund allows you to give appreciated stock or assets like crypto to charity and receive an immediate tax deduction in a high-income year, with the flexibility to determine which charities you want to give to at a later time. Donor-advised funds can also be an effective way to bring your family together and talk to your kids about their giving strategies.

2. Estate planning—if you are in the realm of dealing with the lifetime gift exemption (currently ~$12m if you are in the US), exploring irrevocable planning may make sense.

3. Diversification—diversifying into other asset classes is a great way to mitigate concentrated risk. A lot of people procrastinate this and then never sell if the concentrated position drops.