Unforgiven

Kill three enemies with revenge crits without dying.

This achievement requires the Frontier Justice. Since five achievements is nothing, you'll likely be capable of getting this achievement in no time. To get revenge crits, your sentry gun must get a few kills, then be destroyed. You get two crits for every kill, and one for every assist. Much like Revengineering, this is only possible if you don't die with your sentry gun. You don't have to get all three kills with a single revenge spree, either. As long as you survive to build another sentry gun and get it destroyed, the kills count.

When you farm this achievement, it's easiest to do so with the achievement Revengineering, as they have very similar goals. Have a friend die a few times to your sentry, then let him destroy it. Kill him once for Revengineering, and two more times for Unforgiven. It's that simple. All you need is the Frontier Justice, which is incredibly easy to acquire, thanks to the low achievement threshold.

Note: This achievement title is a reference to the movie Unforgiven, which is one of the best Westerns around. It follows a former outlaw and his friends as they take a job to kill two cowboys that disfigured a prostitute. It's noted for its moral ambiguity and prominent cast, which includes actors such as Gene Hackman, Clint Eastwood, and Morgan Freeman.

Quick Draw

Kill a spy and two sappers within 10 seconds.

It seems like a daunting task to kill a Spy and two of his sappers so quickly, but if you are a good Engineer, this will likely be one of the first achievements you get. When defending a forward base, you will normally have a Dispenser and Sentry. Assuming the Spy saps both, you simply kill him, then destroy the two sappers. It's a very common occurance in normal play, so it's not hard at all to get. Alternatively, you can get it by knocking the sappers off a teleporter, as it counts as two sapper kills.

Farming this achievement means you take advantage of the fact that a sapper placed on a teleporter places it on both the entrance and exit. Get a friend to place a sapper on your teleporter, kill him, then kill the sapper. You'll get the achievement with minimal effort. It goes well with The Wrench Connection, as long as the Spy is disguised, and Fistful of Sappers, as the sappers do not have to be on your buildings.

Note: You can kill destroy the sappers before you kill the Spy, or kill the Spy before you destroy the sappers. It will likely be easier to kill the Spy, then destroy the sappers, as the Spy can always continually place sappers on your buildings as you destroy them.

The Wrench Connection

Kill a disguised spy with your Wrench.

There's no point in farming this. I mean, come on. If you are in any way a competent Engineer, you will get this achievement in your first match of the day. Simply kill a disguised Spy with your wrench. It does have to be a wrench, not the Southern Hospitality, so make sure you are using the default wrench. You will most likely get this achievement in combination with Quick Draw, as you should kill the Spy who sapped your stuff (who is disguised), netting you this achievement, and then kill the two sappers, netting you Quick Draw. If you really want to farm it, go for it, but we assure you that this is the easiest achievement on this list.

Note: This achievement is a play on the title The French Connection, which was a movie made in 1971. Coincidentally, it also has Gene Hackman in a starring role, although as a hero rather than as the antagonist. The film is about a drug trafficking scheme that smuggles heroin from France to America, and follows two detectives as they attempt to unravel the drug network.

Silent Pardner

Upgrade 50 buildings built by other team members.

Time for a grind achievement! In this case, it's a benificial one. You must upgrade the buildings of fellow Engineers, with each upgrade counting once towards this achievement. If you upgrade a friend's sentry to level 3 alone, for example, you will get two credits. You have to get the final hit for it to count as your upgrade, though. Simply working on it with a friend is not enough. Since plenty of people are playing Engineer after the update, this is an easy goal.

Farming this is kind of silly, but if you plan on it, get a friend to play Engineer alongside you. Each of you build a teleporter entrance and exit, and each of you work on upgrading the other's. Once both teleporters are level 3, detonate the exit and repeat. Destroying the exit resets the teleporter to level 1 with minimal effort, after all, and you can work on upgrading the entrance as the exit is building.

Note: This achievement is a reference to the practice of a silent partner, which is the hidden partner in a business transaction. A silent partner is unseen and only referenced anonymously by his normal partner. This is common in shady deals or deals where the silent partner does not want to be exposed to any liability. The normal partner is often a proxy for the silent one in this case.

Fistful of Sappers

Destroy 25 sappers on buildings built by other team members.

Grinding all day. This one is a little more difficult to get than the previous grind achievement, as you will likely be more concerned with your own buildings than those of your fellow Engineers. If you really want it, however, just stick around a friend's forward base and take out any sappers that get placed. You have to be an Engineer as you do this, too. No using the Homewrecker and Pyro to get credit towards this achievement. THe great thing about being on sapper duty is that it leaves the original Engineer free to chase down that pesky Spy. There's no point in farming this, but if you really want to, simply have a friend continually place sappers on a dispenser built by another friend.

Note: Much like the other western movie references on this list, this one covers a famous movie. In this case, it's Fistful of Dollars, which is the first movie in the Dollars trilogy. The trilogy is a series of similarly-themed Westerns directed by Sergio Leone and starring Clint Eastwood. They are often considered among the best westerns ever made, comparable to other classics such as High Noon or Unforgiven.