Headshots, for sure!😜
But all jokes aside, sk1lld and ElliotLH are right this sounds like network issues. The suggestion to provide some video evidence with the network graph turned on is a good one. To do this, from the main screen go to Options -> Network and there switch Show network permance bar and Show network performance graph both to Always. Start playing and record clips of the situations you want to be reviewed and post them here.
Also let us know what platform you're playing on and if you play with crossplay turned on or off.
Unfortunately Battlefield 2042 is notorious for its poor netcode. We've all been there, getting seemingly one shotted, shot behind cover, you name it. It could be your own network, but also somebody else in the server that has a high ping.
And then there's some general game mechanics you need to be aware about. First weapons, if you are using a vault SMG vs a BF2042 assualt rifle, you will loose most of your gunfights if you don't get the drop first on your enemy.
Some class traits also matter, for example an engineer class with a LMG lying prone will turn it into a laser.
Then there are the IBA Armor Plates that the assault class can equip as a gadget, they will provide additional health for upper bodyshots. If you shoot a player equiped with these in the chest you will need more bullets to kill them, you can recognise this by a blue outline on your hitmarkers when hitting the armor plates.
Record your own gameplay and look back at it afterwards is also a tip. Sometimes you think in the heat of a fight you are landing all your shots but when looking back it might be you're less accurate than you thought.