Sniper strenght

Why? Why is it needed?
I'm open to the idea but wondering if you can articulate why it is "needed".

They would need methods of balancing it, because if they just always one-shot that would be terrible balancing. If it was like the Barrett M99 it could be balanced, since you would have to load a round into the chamber after each shot instead of just racking the bolt to pull one from a magazine. Otherwise it is just a lack of skill and ability to get a lethal hit that's your problem at the end of the day.

I meant sniper like it was in BF3 - M98B . It was good snipe rifle

M98B was a 95 damage sniper (at top, before it had falloff), so you're still describing a "lack of skill"-issue. With how the headshot multiplier is being done in BF6, it allows for altering a given gun's attachments to change the performance a bit, like increasing headshot multipliers and projectile velocity. This in turn lets players increase the chance of a OSK based on hitting vital areas with a setup that allows for it, and players seldom keep full hp for very long in combat anyways so the chance of a OSK vastly increases there as well.

A worthwhile gun to not underestimate in BF6 will be the SVK-8.6, even if it isn't a full-hp OSK gun in most cases with its 60 damage, and its 1.35x headshot multiplier stock (you would need a 1.68x for a OSK-capable headshot), but the beauty to using the SVK-8.6 is you'd be able to rapid fire 2 shots on target to get a kill before they can react to being hit most of the time, and that's before you get the level 3 "perk" specialization throughout the match that increases your effectiveness considerably as you can see in the image below.

You can be effective without OSK weapons, you just have to know how to play to the class and play to the primary you're using. Many in the beta realized going for the M39 or SVK-8.6 with a non-glint optic would allow for more total kills by simply being tactical and rapid, as you could account for a potential miss in mere fractions of a second.