4. Over-Zealous NPCs
The unfortunate thing about open worlds that seek authenticity is that NPCs are given their own free-will: it is obviously limited, and they aren't going to rise up like Skynet and turn your toaster against you, but they do have a certain level of autonomy (or at least the pretense of it.) Anyone who has been unceremoniously mown down either in the offline portion of the game, or while foolishly attempting to run across a motorway online will be able to testify to the truth of that. Unfortunately for absent-minded robbers, some of the NPCs in GTA Online will kill you the minute you turn your back on them. This won't happen from an ordinary member of the public, but if you're dumb enough to turn your back on a cashier you've just robbed, they may well pull out a weapon and spray bits off you all over their door before you can make your escape. You should be prepared, and take action, but it's infuriatingly easy to forget that the NPCs can be armed, and going through the process of robbing, only to be killed at the last stage is a good way to incite an immediately, furious rage-quit.
Tips To Avoid Walk out of stores backwards. Or, if you like being chased everywhere by the police, kill everyone in sight and calmly walk out into the street to face the music.