User blog comment:Lisastr67/Questions to me/@comment-24182086-20141016193617/@comment-24458893-20141016194153

You're more likely to get alliance with his enemies

+25% Prestige in battles between you

No Trade Efficiency penalty from embargoing him

+20% Spy Offense aganist them

-33% Diplomatic Power cost for demanding in peace deal

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As we can see, only positive effects