Cheaters?

I'm a 2nd Lieutenant (60) with a 12 Class Medic and a 12 Class Support, which is my go to classes. I'm not an experienced player and not as agressive as some players.
BUT...
How on earth is it possible for a corporal with a 0 class Assualt to take me out with one shot from a SMG MP18, after I emptied a Lewis on his ace...2X? Am I just crap or is there something smelly in the fridge?
Or
A bomber to see me hiding in a building, in Sinai, and bomb my ace 4X? Not just with a machine gun but a bomb. I tired myself in an empty game bomb a building from more or less the same height, with a buddy hiding in the building, and it took a few passes before I got near the target. My buddy is an experienced player and has much more nothches on his belt. He had a go, as well, and he got pretty damn close, but not enough to kill me completely.
When i sniff a "cheater" I generally look for another game, but it would be intersting to hear from other experienced players to hear how to identify a cheater.

The first example, I believe the weapon they killed you with has a higher rof with lower bullet damage, its the high rate of fire that compensates for the lower dmg values, plus your character will be flinching and knocking your aim off a bit too, sounds like you were in a CQB situation where higher rate of fire weapons beat the meatier LMG's.
The second example you gave is just generally a way bombers normally do it, I've often seen bombers drop their payload over buildings to destroy them to reduce the amount of cover available to infantry.

without videos to look at its hard to tell.
the Level 0 could of just been level 100+ player on a smurf account and he was good enough to hit you in the head.
as for the plane bomber, thats (most probably) just inexperence on your part. there are A LOT of 100+ plane flyers who still play this game and can destroy entire teams solo.
i dont know what region you live in (USA, EU, RU) but if you live in the USA there are two community hosted servers that are well maintained unlike the DICE servers that are still running.
I CANNOT RECOMEND ENOUGH TMCG / The Meat Cleaver Gang or BUDzExiles.
if you live in the USA Area, both servers are most commonly active after 8:00 CDT.

Your best bet is playing on community servers that are moderated because the anticheat itself does not work.
Without killcams and replay modes you're mostly ♥♥♥♥ out of luck for identifying cheaters, and even then, you most likely won't even be able to tell really good players apart from subtle cheaters who are smart about it, meaning the ones who don't just one-shot everyone from other side of the map.
There are also things like damage multiplier hacks that, again, you will need a detailed knowledge of each and every weapon, their range and TTKs on all distances to even begin to estimate whether someone is using, say, a x1.2 setting.

Thanks for the feedback. Admittedly, my experience is somewhat lacking. I'm still learning the finer nuances of each weapon and class as I progress. I have only been at Battlefield for two months and found it immensely good escapism...considering my age.

1 and 5 are full of them man