I hate agreements too. They fight wars on your turf. They drag you into wars just to screw you.
You're CivA. CivG attacks CivB. CivB asks you to join the war against CivG. You do and are cleaning house, annexing massive territory. Civ B settles with CivG. You keep fighting because CivG won't talk to you. CivB makes trade embargoes against you. You eliminate CivG. The embargoes end because you've got luxury resources the rest of the world was trading with CivG.
It continues. CivA, trying to better your relations with CivC. You form a MPP with CivB to watch your back. CivD declares war on CivC. CivB then allies with CivD against CivC. CivC dares attack a unit of CivB. You are then obligated to go to war against CivC unless you want to go to war with CivB, CivD and have your reputation tarnished forever around the world.
So since your reputation with CivC is tarnished forever you decide to take a couple of cities. CivD settles with CivC. CivB continues the war. CivC asks you for a peace agreement. You agree to it. CivB is now annoyed, but you still have your RoP with them.
CivB is winning the war and is now the most powerful in the world. You build up your military. Then they go Communist, and you start making major power and cultural gains and overtake the lead. You just got a better deal selling ivory to CivF, so you want to renegotiate your ivory trade deal with CivB. Remember you just got 150 gold per turn from CivF for this item. CivB won't give you 1 per turn. He tells you, "You have broken deals in the past, and I will never deal with you again."
You get tired of them pounding CivC for some 40 turns, so you remove your RoP. CivB is now furious, as is CivC. You get an RoP with CivC just because you want to watch the progress -- "Against my better judgement, but I'll agree" CivC says (furious).
CivB violates your territory, and you ask them to leave. They declare war. You form an alliance with CivC. They agree but are still furious. CivB breaks CivC's back, and your troops arrive and pound CivB's forces eliminating a stack of 10 infantry. CivC loses another city. You counterattack and take the city. The citizens rejoice! You pull your troops out and go to the diplomacy screen and outright give the city back to CivC for three reasons: you don't need it, and it's so far away from you the corruption is catastrophic, and it was theirs in the first place.
CivC remains furious with you. Moral of the story: No good deed goes unpunished.
If you retake their cities from CivB and give them back to them enough times, will your standing with CivC ever improve?
In the end, it may be necessary to crush them all.