9. Random Killers/Spawn Stalkers
GTA Online is not meant to be a cake walk, and it's certainly not designed to be the sort of warm and welcoming community that attracts Sims players, but being killed for no damn reason, and with very little warning is still one of the most frustrating parts of the entire game. It's a criminal community, so you're bound to find players who literally don't care who they're knocking over or killing, but there should be some honour among thieves, especially if all you're doing is scoping out an area, or going on a shopping spree. And then of course there are those who actively seek to kill you as and when you spawn, either by hanging around hospitals like a bad stench, or by mercilessly tracking you down every time you spawn and killing you simply to troll you into a reaction. The exception perhaps - though still massively annoying - is the player who sets traps. If you're dumb enough to get into a suspiciously attractive car left parked in the open, you deserve to be blown up by the inevitable car bomb that's probably hidden within it.
Tips To Avoid For the spawn stalkers, immediately entering Passive Mode is probably the best option, if you really must, or you could report them, though it might not be immediately successful. Or band together with others and form a posse to give the agitator the comeuppance their behaviour deserves: such as repeatedly running over their head. The random killers are difficult to plan for, the key is simply not to make yourself a target. Do no excessively use Passive Mode, as that's for cheaters and children, but tips like not walking everywhere, or simply going Falling Down and murdering everyone in sight are possibly your best options. The latter will come with inevitable consequences, of course.