DAILY DRIVER: Drive into / shoot a civilian on a segway.
TRUCKSTOPPER: Destroy an armored truck [the round boss.]
ATHEIST: When Jesus appears & summons zombies, dodge every zombie on the field and never hit a single one.
UNDERTAKER: When Jesus appears & summons zombies, ram your car into every zombie on the road; no it doesn't matter if one manages to hop onto the car and attack Deimos, that one also counts, provided you knock it off the hood of the car at some point.
SHARPSHOOTER: An "Unstoppable" kill combo requires you to kill off all of the agents on the road in one sweep; there cannot be any stragglers left behind by the time a new swarm of agents appear to attack you. You need to score this combo while using and only ever using the pistol; you won't score this achievement if you swap off from using the automatic rifle with the pistol during a sweep. Do not fret if you miss one agent before a new swarm appears, if you kill off the straggler in addition to the new swarm, you'll score this achievement. If you actually make a serious attempt at getting the Improbability Drive achievement, the Sharpshooter achievement is essentially a package deal in conjunction to that; you'll eventually get it without really trying by that point.
IMPROBABILITY DRIVE: This achievement basically requires you to beat the game, that means I have to write a strategy guide detailing the games entirety.
In order to score this achievement, you have to disregard all of the other achievements, because by this point they serve as nothing more than distractions that'll eventually sap your health to nothing by the time you reach the 6th round. This means that you have to disregard; hitting civilians, dodging/hitting zombies or getting an unstoppable kill combo with the pistol.
You'll also have to learn to neglect targeting anyone, don't concentrate on one agent and stalk it until it dies; this is a good way to get other agents to jump onto the car and beat dents into it, or worse, fire bullets at it. Whoever's in front of you is in front of you; no exceptions, not even with the armored vans.
The reason why is because you'll need to pay the majority of your attention to dodging zombies, parachuting agents, agents leaping off of their bikes, agents leaping out at you from the back of armored vans, boulders, road blocks, yellow barrels & bullets.
Dodging parachuting agents is somewhat tricky, but remember, just as long as their parachutes are attached, you can pass under them freely without trouble. However, the point in which they detach their parachutes & begin free falling is the point in which you need to avoid them like the plague.
The Zombies are less trouble because they really don't do anything harmful beyond disabling Deimos' ability to shoot. As long as you don't directly drive into them, they'll either pass by or catapult into the far distance. But should the Y axis of the car align with the Y axis of the zombie, prepare to shake your mouse vertically.
If you get a more powerful gun such as the shotgun or the grenade launcher, don't waste it frivolously on the regular red agents, use it sparingly on either the A.T.P. agents or the armored vans. The red agents can be knocked off simply by ramming into their ass ends or by driving into their sides [X axis] until they collide with the wall/pit. The A.T.P. agents however, cannot be killed off so easily; although they really don't pose much of a threat until they align with the car's X axis, they cannot be killed unless you use a fire arm. Avoid using shotguns, automatics and grenade launchers on them as much as possible when the armored van appears on your meter at the top left, because when they do finally appear, they're a bitch to kill and they make it harder for you to survive by either opening fire on you, throwing red agents at you or by dropping explosive barrels onto the road.
REVIEW: My only real complaint is how much longer the rounds get as you progress, which would be fine if there was save points or checkpoints, but I'm expected to beat all 10 in just one sitting. BS.