The early warmongers are not very dangerous even if you 90% expect they declare war on you. You kill off some of their stacks and then take one of their cities and you get peace. Sooner or later they fall back in techs and they no longer be harmful for you. Shaka, Monty, Ragnar, Alexander... all of them are such kind of freaks.
But then lets take hannibal, justinian, zara, mehmed... they have their economy grown up and then come for you... You engage them 20 turns and then when you even get a peace their best friend wang, gandhi or mansa has electricity, radio and mass media when you get physics because for enaging wars you had path for rifling/assembly line. And then you see Broadway has been built in far away lands, 2 turns later Rock'n'Roll has been built... and then Hollywood + bonus Eiffel Tower. Then your feel that game is almost lost because of you lose by culture... if you are lucky and get internet first and then raze some of legendary cities then you can win but otherwise I have to restart.