Backstab 3 Snipers in a single life.
A great achievement to get, and also an easy one, given the right map. The map in question is, of course, 2fort, thanks to the set-up of the balcony. Head up through the enemy base until you are coming in through the balcony entrance. There should be two or three Snipers sitting there and shooting. Take out your knife, and bam bam bam, you have the achievement. Especially easy there considering the radius of the backstab (180 degrees behind the Sniper) and the layout. Most Snipers just stand in a line! In fact, you could even get You only Shiv Thrice by doing it this way.
To farm this achievement, have up to three friends be Snipers. The reason for three friends is so that you can arrange You Only Shive Thrice, if you want. You can do it with only one, though. Have your friend(s) stand still while you do your thing. With one friend, you will get Melbourne Supremacy (as you will dominate the Sniper) and with three friends you will get You Only Shiv Thrice.
Note: You have to get all three backstabs without dying, as the achievement says. However, they do not have to be in order, or even remotely close in time to each other. Just three Sniper backstabs without dying.
Stab an enemy to death while under the influence of Jarate.
This one is one of the hardest achievement in the entire pack. Why, might you ask? Well, Jarate shorts out your cloak and exposes you as a Spy. Chances are tha tthe Sniper knows you are a Spy and will be chasing you down with one of his weapons to kill you after smashing the jar of piss all over your face. So what do you do? Well, you can try and outmanuever the Sniper, but you will probably die to the Kukri. The best method to obtain this is to simply turn around and backstab somebody else! You don't have to backstab the Sniper that hit you. You can do anyone, as long as you have been affected by Jarate.
To farm this, have a friend splash you with Jarate. Then backstab him. You might have him splash you again while you are cloaked and let him kill you with his Kukri afterward for the achievements Jarring Transition and Jarate Chop. There's no real achievement you can farm alongside this one, unfortunately.
Note: You must be coated in the urine of a Sniper in order to get this achievement. That means you can't jump in water to wash it off before stabbing somebody. This achievement is also a reference to the term "wetwork", which is a euphemism meaning "assassination".
Who's Your Daddy?
Headshot 3 Scouts with the Ambassador.
This achievement, much like Wetwork, is relatively hard as well. It is difficult enough to headshot Scouts as a Sniper, so you can imagine what it must be like to try and get it with the Ambassador. Our only suggestion is to simply shoot at Scouts and don't bother trying to get this achievement except by luck. Scouts move far to fast and deal way too much damage to you to engage head on, and the Ambassador doesn't have good range compared to the Sniper Rifle.
To farm this achievement, get your friend to stand still and do a standard double-tap: one shot to the torso and one shot to the head. The shot to the torso weakens the Scout enough that the single shot to the head will take him out. Unfortunately, this achievement can not be farmed with other achievements, as it is the only achievement that involves Scouts or headshots of somebody besides Snipers.
Note: This achievement is a hilarious reference to the Meet the Spy video, where it was revealed that the Spy had seduced and had sex with the Scout's mother. To add insult to injury, the Spy fell in love!
You Only Shiv Thrice
Backstab 3 enemies within 10 seconds.
Another exceedingly easy achievement, this one has you performing a quick succession of backstabs. The easiest way to do this is to get behind a large enemy group, disguise and decloak, and run forward. As soon as you are in the thick of things, start backstabbing. If the group was sufficiently large enough, you'll get the achievement without issue! You can also attempt this with a batch of Snipers hiding in battlements, if you want. Make sure they are reasonably close to each other, though.
Farming this achievement functions exactly the same way as Triplecrossed. Get three friends, preferably Snipers, and have them all stand in a line as you backstab them in quick succession. You will net yourself Triplecrossed! Alternatively, have two friends be Medics, one be a Heavy, and have each of them heal one of you (one Medic on the Heavy, other on you). Disguise as a Medic, backstab the Medic and Heavy pair, and then backstab your own Medic. Identity Theft, Insurance Fraud, FYI I am a Spy, May I Cut In?, and You Only Shiv Thrice all at once! It's a great chain.
Note: The name of this achievement is another obvious James Bond reference. In this case, it is to You Only Live Twice, the second to last Bond film to star the original actor Sean Connery.