Crackdown 2

I found this achievement easiest to obtain solo. Pick the map "North Green Bay" and set the difficulty to fragile. The strategy I used was fairly simple:

Make sure to always grab a power weapon at the end of each wave at the blue ammo box; whether it be the Rocket Launcher, the Grenade Launcher, or just another assault rifle they will all come in very handy. Also, do not forget to replenish your grenades if they appear (they almost always do. Don't bother with the proxy mines). Each wave, try to utilize all of your grenades and power weapon ammo. It speeds up the wave magnificently. However, don't simply rely on those to complete the wave. Start each wave by hovering in and throwing your grenades and shooting rockets/grenades in, then switch back to your rifle and headshot the remainders.

Never bother meleeing or anything else other than simply shooting/throwing grenades. Also, it is very, very important not to die. While it isn't a total game breaker if you do, it will however slow your pace down significantly. Try to stay alive the entire time and ALWAYS keep moving, never sit stationary and if possible, try to use your boosters as much as possible. Of course, watch your time and make sure you're at a good pace--if you don't die, however, the time should hardly be an issue.

Using the simple tactics provided above, I was able to achieve 1,000,000 points by Zone 3, Wave 9. It took 28 minutes, and I ended with a 7x multiplier. Again, key things are:

-Pick up and use power weapons/grenades each round for clustered enemies.
-Don't bother meleeing or anything else other than shooting.
-Maintain movement and thruster usage at all times if possible.
-Most importantly, try your hardest not to die. It will reset your multiplier and take away 30 seconds of your time.

Overall, this achievement is actually very easy to complete. Just be competent, have situational awareness, never stop moving, and DON'T DIE. Best of luck to you, Agents.

Not the toughest achievement. Deluge is a timed event: time continuously runs down and you get extra time after each round as well as the occasional time bonus. Your run ends when either all players are dead, time runs out, or you finish the 50th round. I did this with one other person, which I think is the easiest way. The more players you have, the fewer points are available per person, since there are a fixed number of enemies. You could easily wind up finishing an entire run without anyone in a three- or four-person group getting to 1 million. On the other hand, by yourself it's much more difficult to finish the rounds in time. Maybe it's possible for some of you, but I suspect I would not be able to last much past Zone 1 on my own - it just takes too long for one person to clean out the entire round. You also have to regenerate if you go down solo, which slaps you with a very significant 30-second time penalty. If you have a teammate, they can revive you, which not only saves the time penalty but gives them a 5,000 point bonus.

Not that you want to die often. The best way to stack up a significant score in Deluge is with the score multiplier. It goes up as you make more kills, but resets if you die - even if you get revived. When I popped this achievement, I died three or four times. In fact, both of us did, and we still both passed 1 million in the same run. It's not game-ending if you die, but obviously getting 6 or 7 times more points for every kill is a drastic improvement. It's a bit depressing when the multiplier resets to 1, so the key is keeping the run going at all costs. With two people playing, and roughly keeping the kills even, you will be doing well to pop the achievement before zone 5 starts. We both got it in the middle of zone 5 (around 5-5 and then 5-8 if I recall), although on later playthroughs I was able to break a million earlier than that by not dying. Keep in mind there is a time bonus at the very end, so if you do happen to finish in the high 900s, don't quit out until you see your final score.

In later rounds, it can be difficult to avoid dying with all the rocket and flocket launcher action around. Keep moving at all times, and target those people first. They're usually up high, and the limited ammo for better weapons you get between each round is best used on them. Once you've cleared out the rocket launchers, your biggest enemy is time. We usually started at separate sides and worked toward the middle; this minimizes both the number of wasted shots and the number of times a teammate's errant shot sends you flying across the screen. I relied heavily on the enemy positions shown in the radar circle rather than using the ones that show up in your main view. The latter type can be very misleading if the enemy is not directly in front of you.

I found myself doing quite a bit of ground-pounding and thruster-frying. Note that the thrusters themselves, which send out a wave if you activate them while full, will immediately kill some of the lower-powered enemies near you, especially in the earlier rounds. A ground-pound finishes off most of what's left. If you are shooting, then remember to target the head when shooting at heavily armored targets. Cars go quickly if you are on the driver's side and target the gas tank - much faster than any other way to take them out, and a lot more points than if you just kill the driver. Grenades are good if the vehicle is stationary, but communicate with your teammate if you're tossing grenades about. I found grenades were most useful at the beginning of each wave to thin out the biggest mass of enemies at "my" end of the group.

The helicopters, which you get if you have the viral achievement (see the "Project Sunburst" achievement), I found most useful in the earlier rounds. The rockets don't target well enough to quickly take out a particular enemy, but are very well-suited to large groups. The problem in later rounds is that it gets very difficult to take out the opposing rocket launchers before your chopper gets destroyed. I would recommend using them from the beginning, although keep in mind that some of the waves have a large number of enemies under an overpass (limiting the chopper) or in a mountain cave (making it nearly useless). Make sure and stay out of the way of your partner - working from opposite ends and keeping an eye on their position - because in the early rounds the only likely way you will get killed in a chopper is if your buddy takes you out or you run into something. If only one person is in a chopper, they should be concentrating on groups of people while watching out for the one on foot. The other person should be hanging out on the periphery and cleaning up those people that aren't easily accessible from the chopper while trying to stay out of the line of fire. Stay airborne as much as possible, using the thrusters, but staying close enough to do damage to the singles that the chopper hasn't gotten to yet. It should go without saying, but: communication is important. It's easier to avoid blowing your partner up if you know where he is headed. In later rounds, when you don't have the chopper, you'll want to use the jump points that appear after you finish the round to move between waves. They usually are much faster than getting there with thrusters/flysuits.

In most rounds you should aim for finishing with slightly more time than you started with, so that when you have trouble with a round it doesn't end your run. Keep communicating with your partner and watch them on your radar so you don't interfere with each other - mainly, keep moving, keep killing, and stay out of your partner's way.