by TheLeviathanMake him feel like he won something. Make the other feel like the winner and any aggression that they have will be directed elsewhere. Now, if they feel like they've won, but also think that there's more they can get out of you, then you will get the opposite effect. You need to leave him with something but also make it apparent that there is nothing more he can get out of you.
But that idea should get your started.
I approve of that. A five-digit cheque (or rather the equivalent in cash) usually works like a charm, with no hard feelings incurred.