Never ever would I fold KK in cash or tournaments. The
odds say you only get dealt KK or AA once every 110
hands, So AA once evert 220 hands approx. KK has so much
equity against every other hand less AA but even against AA, KK still has 20% equity / chance to win in show down ie you are all in and see 5 board cards. And even the pro's will tell you it is generally a mistake to fold KK pre flop as it is too difficult to figure out if they are 4 betting you with AA or lesser hand. Having said all that if you know your opponent is a nitt that only plays the top tier of hands and reraises you ie 4 bets you (you did raise right) then I might be able to find a fold but that's playing the player. I would ask them if they would show their hand if I fold and try to get a tell are they excited nervous calm etc. And you should not slow play rather fast play these premium hands. Don't fold these in online games too many idiots always reraising you just get it all in. They all think its correct to 3 bet and 4 bet everything just get it all preflop especially if you are shorter stacked. If I have a deep stack then I might just call a reraise and evaluate on the flop if an Ace comes or my opponent is giving me alot of resistance then try to check it down or check call the turn and river or fold they likely called or reraised you preflop with an Ace ie AK/AQ especially if they are in EP like UTG or UTG plus 1 and they are giving you resistance. Good luck and great ??.