At those ranges all but the last three really need apply. 12.7x99mm BMG was originally developed as a ant armor round for the M2 and was used for the main armament of American fighter aircraft until the late 1950s.
The Russian 12.7x108 also used by the PLA is even more impressive both it and its American cousin were used as antiaircraft guns and were rated to punch through fighters at 2 miles in a dog fight.
The 14.5mm round is used by at least 2 rifles and is even bigger and again a antiaircraft round.
The 20mm round is used in a South African rifle and is the same round used in the USNs Phalanx.
All designed to destroy non organic armored targets at extreme ranges. Yes the latter two are Cannons! But they have been employed as sniper weapons.
I forgot to add the .408 Cheytac as well which differs as it was a purpose built long range sniper round.
The 12.7mm rounds and the Cheytac are employed widely in so called "Ant material rifles" like the Barret M107A1 and the Chinese AMR1 they are man portable to a degree and employed with sniper units world wide.
Are all these high cal rounds accurate enough to be used against man sized targets at 2miles+ ranges though?
Sure, most of them were designed as anti-aircraft rounds, but they were also designed to be fired in full auto mode at far larger targets.
Anti-material rifles are primarily designed to hit high-value soft to semi-armoured equipment, not people.
Sure, you can hit man-sized targets, but can you do it at 2miles+?
Seems to me like you got a paradox.
Dedicated sniper rounds are accurate enough to be worth using at such extreme ranges against human targets, but lack the stopping power to still defeat modern body armour at such ranges.
High cal AMRs have the punch to obliterate someone even at those ranges, but are they accurate enough to make sure shots anything more than pot shots?