I'm pretty sure the titled has triggered some already but I stand by it.
The hardest play style in the game imo is NOT the aggro sniping, although it comes really close.
This a playstyle that requires far more concentration, and skill to pull of, however pulling it f is probably the most rewarding....
And that is m1900 slug sniping... It is the definition of a skill cannon. It instantly kills cqc, if your accurate it will almost always 2 hit kill lightning fast. You can fire both barrels for instance kill up to 50m. You can snipe with this gun up to 60m effectively. So it has raw ttk + range to kill med range.
However it is the most unforgiving gun on the planet. Miss in cqc you die, ads is far more inconsistent than hip fire at range. I find better success hip fire sniping, which in honesty is the v hard, had some pretty hilarious clips hip firing headshots 40m away. It's a slug so you have to be dead on, and it doesn't move as fast as bullets
Pair this with obrez and you have imo the skill cap for gamers. I have to be absolutely on zone to try this out.
Ironic how the same class has both the easiest and hardest playstyle in the game.