There are few ways to do this depending on how much you want to cheat
The intended way: Choose your favorite civ, make new save files often so you can load back whenever you make a mistake
The less intended way: Choose your favorite civ, make it continents duel so you only have one competitor and you can extract the resources of an entire continent with no competition.
The even less intended way: Play duel pangea against Venice, go into the settings and remove all city states so they can't expand
The cheating way: Download a world edit or cheat mod, give yourself all the tech, place a giant death robot next to their capital, save the game, load back into it without the cheat mod on (mods disable achievements) then take the capital in that game.