Not sure why you would consider LHR or similar as a "worst airport". Plenty of longes, great duty free shopping, good food such as Caviar House..etc..etc..

You should try flying to some small 3rd world airport to get to know the true meaning of worst. Try no air conditioning, loud, dirty, no queing up for anything, just one mad free for all, the food will put you in hospital for a week,the only way to get anything done is by inserting a few bills in your passport...one visit to such squalor and LHR will seem like one un-ending Molton Brown Spa...