Damage Mod and at least sometimes aimbot.

68:8, 59 from AEK, 8 or 9 from handguns, 0 HS ribbons, 183 hits.  That's .37 kills/hit.  He shouldn't get more than about .25 from that, or .35 if every non-AEK kill was a one-shot, but that can't be since he has no HS ribbons and was using handguns when he wasn't using the AEK.  http://battlelog.battlefield.com/bf4/battlereport/show/1/906449926622065472/999158567/

86:14, 85 from SAR21, 27-29HS, 204 hits.  That's .42 kills/hit vs max .35 possible.  http://battlelog.battlefield.com/bf4/battlereport/show/1/906009071536732800/999158567

17:1, 17 from Groza-1, 0HS ribbons, 43 hits.  That's .40 kills/hit vs .34 possible.  http://battlelog.battlefield.com/bf4/battlereport/show/1/906052604348956096/999158567

55:11, 50 from SAR21, 24HS, 114 hits for .48 kills/hit vs .43 possible.  http://battlelog.battlefield.com/bf4/battlereport/show/1/905958075226837696/999158567

61:12, 57 from AK12, 35HS, 133 hits for .46 kills/hit vs .45 possible and 57% HSK.  http://battlelog.battlefield.com/bf4/battlereport/show/1/905952086545060544/999158567

And then there are multiple BR's like this one, where he has 1 kill per hit from sniper rifles, yet doesn't manage 100% headshots...  10 kills, 10 hits, 1 HS ribbon:  http://battlelog.battlefield.com/bf4/battlereport/show/1/906431817509024576/999158567

Brought to my attention by a combination of his in-game stats and players complaining...

  [06:13:29] XXXXXXXXXX > fuckin damage hacker bernardoogg
  [06:42:13] YYYYYYYYYY > Bernarddog just sniped me through a huge wave
  [06:42:45] YYYYYYYYYY > I'm not normally the type to call hacks but copnsidering his score and what just happened
  [06:42:48] YYYYYYYYYY > kinda obvious
  [06:52:15] ZZZZZZZZZZ > any admin on::: Bernarddog is cheather!!!

Players pegged it.