A lot of these are going to be pretty hard simply because this game does not have a lot of player support. It can be impossible to get enough people into a match, let alone do what the achievement requires. Because of this I would suggest looking to the boosting thread to find people. If you are host, meaning you try to find a gametpye and no one else is in the room, just press start to instantly start the match! (Thanks Shadow Austin 317)
SOME BOOSTING METHODS FROM upindat:
SOLO: Black Box is 1420 XP for 2 minutes alone if you are working to hold the case, 1500 for destroying it but it's a lot more work. Icarus will net you 1200 XP for about the same amount of time.
4 PERSON DATA MINER: Can really be done in any mode that is time based versus kill # based. Simply ignore the actual objective and go for kills. Bonus points can be acquired for killing people in the air (Clipped Wing), ADS Sniper (Counter Sniper - Has an achievement!), and Last Bullet. I would suggest going for 10 and then switching. 10 kills is the top streak and also 10 kills for dominating. Then when someone else takes over they will get a huge bonus for killing someone on that size of a streak.
Shaken, but not Stirred - 10 Public Match: Survive 50 explosions while using Reactive Armor.
Reactive Armor is a level 42 unlock in Gadget 2. Then run up to grenades and mines and hope you survive.
Return to Sender - 35 Public Match: In Bomb Defuse disarm the bomb and plant it at enemy base without getting killed.
Then "simply" let them plant, defuse, and plant at their base. All without dying. If no one else comes in you can do this easily with a friend 1 v 1.
Omega Virus - 15 Public Match: Kill an enemy who has completed the campaign or who already has this Achievement.
First achievement I unlocked. It will unlock immediately on killing the enemy. There is no way of knowing if they have it or not but it's already pretty viral.
Midas Touch - 15 Public Match: Win a match on Main Vault, Smelting Room and Loading Bay.
This can be any game mode. Just vote for these maps when they come up. It will unlock at the end of the match in which you win your third time.
Laser Eraser - 15 Public Match: Win a match using only laser-based weapons.
Under Weapons - Submachine Guns - Moonraker Laser is unlocked at level 30. Also Secondary - Machine Pistols - Laser Pistol, but this is unlocked at Specialization level 4, a lot later than lvl 30. You only have to be on the team that wins, not get 1st place overall.
Alternately in Legends, Hugo Drax starts with the Laser Pistol. The difference being you would have to win a FFA with just the laser pistol. Much harder solo than as a team, but much sooner time wise to start trying.
Hold the Line - 30 Public Match: Win a Data Miner match without being killed.
You need to to be the first to get to 100% completition or be the highest when time runs out. You're uplink goes faster the more cell phones you pick up from dead enemies, whether you killed them or not. A full match is a long time to go without dying. If you can get a Data Miner room where noone else is in it (very likely) that will make you host. Simply press start to immediately launch to match. People can join but hopefully you will have a HUGE headstart. You come up on the map when you hit 60% completed so be careful. Also make sure to move around a bit so you don't get kicked for inactivity.
Disarmed and Dangerous - 20 Public Match: In Escalation demote an enemy who is armed with the RPG.
Escalation is a weapon progression gametype that requires 4 people to start. Each time you get a kill, you gain a better weapon. The RPG is the last weapon before winning. To demote someone you have to melee kill them.
Counter-Sniper - 25 Public Match: Kill 50 players while they are aiming down the scope of a sniper rifle.
You can check your progress under Agent Record - Combat Ability. The Combat Ability to track this called Counter Sniper.
Danger! High Voltage - 10 Public Match: Get 25 electrocution kills as Zao or Gustav Graves.
Once you unlock Manage Loadouts at lvl 6, select Zao in a Loadout under Legends Character. His melee does electrical damage. You need to play the Legends game type for the unique ability to matter. Legend requires 4 people to start a match. Although there is no electrical Combat Ability to track you can look at your Melee Kills when you start your Zao run.
All the Time in the World - 40 Public Match: Play for more than 24 hours.
Your time played is tracked at the bottom of your Agent Record.
Unlocked and Loaded - 5 Public Match: Reach level 6 (Midshipman).
00 Agent - 30 Public Match: Reach level 50 (00 Agent Grade 0).
A Farewell to Arms - 50 Multiplayer: Enter 00 Specialization.
Level 6 is 15,000 XP. You need 1,009,750 experience to reach level 50 (Thanks SpongebobRoundpants). 00 Specialization is the 007 Legend's version of Prestiging.
FYI - I have 142940 XP (Lvl 18) at 5h 49m