Potential allies don't aid you. Flaming Fist appear out of nowhere and attack you. Merchants won't sell to you.
But all of this is exactly as it should be. The Forgotten Realms is very much a 'good' setting overall where good generally prevails. So things being this way is what is realistic and to be expected. Being good involves consequences; being evil should also involve consequences, including especially everyone coming for your head.
