How to force Human Player to surrender?

Hi,

I wish it wouldn't have had to come to this. But I was lanning eu4 with a friend, and he gets into a vassal independance war which I joined. After my friend was defeated, he refused to surrender or accept any peace deal. Luckily the AI would eventually send him something he agreed upon,
However he immediatly truce breaks and declares war upon me (out of spite?), and demands his lost territory back. Natuaraly, he is promptly defeated but this time he does not accept any peace with me.

He let his -3 stability, 3xbankrupt completly occupied country run for 70+ years, while I deal with rebels, a rising call for peace, war exhaustion and in the midst of it all several other wars I have to manage because of this moment of struggle and weakness for my own country. It was honestly the worst piece of gameplay I ever experienced just because he was so, so petty to accept his defeat and any peace deal (I was even giving him very, very beneficial peace deals like 1 province or white peace).
It was such a struggle, mentally too, to play against someone with so much spite and hate and ' cartman' like strategies.

My ultimate question is: How can a Human Player force or trigger a peace deal with another Human player who physically refuses to do so?