Advice on Breaking Up with Co-Founder Ahead of Vesting Cliff

I started my start-up as a solo founder. After 1.5 years of working with contractors and wearing all the hats myself, I started working with a partner who I hoped would take on the COO/"Integrator" role to my CEO/"Visionary" to move things forward.

We have been working together for about 8 months and during that time it has become clear that he's not the right fit for me as a long-term partner.

We have an advisor agreement that would grant him an advisor share of equity for his contribution in our first year working together. After the first year cliff, he would be on track to start vesting a much larger co-founder equity stake. I want to end or alter our relationship before we reach that cliff.

While I'm quite sure that our legal agreements cover me, I wanted to see if anyone who has gone through this has other advice on the best way to end this type of relationship in a way that avoid other problems, respects my partner as a person and leaves the door open to working together in the future in other capactities (e.g. advisor).