*UPDATED 14/10/15 to Reflect Robbery Expansion DLC #2 and patch 1.0.3*This achievement, just like all 3 other "10,000 Kill" achievements may seem like overkill, but they are very doable and the combined completion time of all 4 is not only faster than Gears of War 1 "Seriously...", but also a lot less stressful and easier. They only require 4 people vs. 6, you can rent servers and kick randoms to your hearts's content, and respawn times are insanely faster allowing for higher kills/minute (7-8 vs. 1).
No Current way to track your overall class kills on battlelog, but if you add the kills with the following weapons/gadgets you will get a rough estimate. It is only a rough estimate as you have no way of knowing which class was used with non-class specific kills totals. (i.e. Frag Grenades, T62 CEW, etc.). You can find these stats on the battlelog website under the stats tab and then by selecting weapons.
PRIMARYM416
M16A3
RO933
G36C
AKM
AKS-74U
ARM
SG553
CAR-556
ACWR
L85A2
RPK
F2000
MDC
FAMAS
GADGETSDEFIBRILLATOR
REVIVE
M320 CS GAS (Launcher)
M79 CS GAS (Launcher)
SECONDARYG17
92FS
CZ-75
P226
THESE 10,000 Kills achievements can be obtained on any map and you are not required to have all 10,000 Kills in new maps only. The tracker for these kills however did not begin until you downloaded the 1.02 patch which was release at the time of the first DLC. Therefore any kills prior to the first DLC release date do not count towards your 10,000 Kills achievements.
This achievement, just as the other Criminal Activity achievements, will unlock mid round instantly as soon as the requirements are met and you do not have to wait until the end of a match for it to unlock.
Some rumors have suggested the achievements will be nerfed in the future and made easier, but I have not seen any official visceral announcement of this.
*UPDATED* - As of 13/08/15, Visceral has stated on twitter that they are not able to nerf the 10,000 kill achievements.
https://twitter.com/zachulon/status/631962147120025600BOOSTING This achievement will take many hours. 4 players / boosters are required to start a match.
Solo boosting with 4 boxes should net completion of each achievement in about 10 - 12 hours or 40 - 48 hours for the combined 4 achievements. Solo 4 box boosting I was able to average approximately 900 kills per hour. Boosting with 3 partners should take less than 4 times as long as solo 4 box boosting. The discrepancy ratio between solo and having partners is due to solo boosting would be on Team DeathMatch (slower respawns) unless you purchase additional DLCs for your secondary accounts in order to have access to Bounty Hunter (faster respawns). *UPDATED 14/10/15 for Patch 1.0.3* One of the patch contents is a nerfing of the Spawn Beacon "Satellite Phone" which now has a "cool down" timer implemented. This effectively makes solo 4-box boosting nigh impossible unless you have 4 tvs set up with the xboxes in order to spawn the bots on actual squad members rather than waiting for the cool down timer on the beacon. 4 Player boosting is still viable , just make sure to keep 1 player on the dying team alive to allow for other players to spawn in quickly. As long as this rule is followed 4 player boosting I would still estimate to take 40-50 Hours per achievement for all 4 boosters, but solo 4 box boosting I would estimate is easily doubled in time to 20 hours per achievement unless you have 4 TVs.
Finding an empty server is not a problem , but randoms will generally join after a short while. Quickest would be to rent a server and play on bounty hunter game mode with lowest possible respawn times and player health set at 75% (lowest and allows for 1-hit knife kill slash), max time. Have at least 2 players have a respawn beacon ("Satellite Phone" found under mechanic class) unlocked. At least 2 with this beacon so that there will always be one regardless of whose turn it is to do the killing. Move 3 players to 1 team and have the 4th player constantly kill respawning enemies with knife slashes (quickest) or whatever they choose. As long as the bounty coin that is dropped by the killed enemy is not picked up the score will remain 0 - 0 and you can kill like this until the time ends for match. Switch it up every few hundred kills to another killer. 4 Players should be able to boost 400-500 kills / player in 2 hours time as long as everyone is present and respawning as quickly as possible or have their turbo controller set to rapid fire 'A' when it is not their turn to kill. So solely going for this achievement will take roughly 40-50 hours of boosting.
BOOSTING SIDE-NOTE - There is such a thing as "Killing too fast". Sometimes if you kill too soon after the spawning player has not "settled" down or fully spawned you will appear to get the kill (including the top right kill feed) but the kill will NOT appear in the middle kill feed. These kills appear to count towards the assignments BUT are NOT logged by battlelog. So you may have a discrepancy in your stats (i.e. completing an assignment that required 100 kills with a particular weapon, but battlelog only saying you have 90 with that weapon). It has been confirmed on the XBOX One version of hardline that these kills will
NOT count towards the achievement. As they are not logged by battlelog, the odds are they do not for the XBOX 360 version as well. Therefore, it is a good idea to slow your killing down if you are experiencing this often. On TDM, I was able to 4-box boost and kill the 3 bots 6 times per min each before I would encounter the kill-glitch if I attempted to speed up to 7 times per min each. Personally I theorize that the game does not like a duplicate kill in the kill feed simultaneously. I.e. FNSUITE GHOST [SCAR-H] BOT 1. So I would not be able to have a kill against BOT 1 count again until the kill feed entry for BOT 1 disappears.
LEGIT Playing completion time I would estimate at 100 hours + per achievement for the average skilled player or 400 hours for all four achievements.