Asphalt Legends Unite

As of the time of writing this guide, there are a total of 1,440 flags available in career mode. While you only need to get 800 for this achievement, this will still take you around 60 hours at least. This is because you will continually reach points where you don't have any cars good enough to keep winning races, so you're stuck playing other modes in the hopes of getting car blueprints.

As for the flags themselves, every race in career mode has 1-3 flag challenges. You'll get one for winning/beating the race always, but then some races have 1 or 2 extra challenges. Many of the extra challenges are extremely straightforward, but it's worth highlighting that you do NOT need to complete all flag challenges in a single attempt. Each flag is unlocked independently. So your primary goal should be to win the race. Once you've done that, if there are any additional flag challenges you didn't do, you can then replay the race and go for them without worrying about winning. This is especially useful if you've got a tough race with a Class A or S car whose gas is valuable. Beat the race with your best car, then replay the race with a low quality car you don't care about to mop up whatever flags you're missing. This allows you to save gas on your good car without compromising your chance of winning the race just to complete other challenges.

I'll highlight a few flag challenges with some tips, but only ones that I feel I have some useful info to provide. Many of them are very straightforward, such as drifting X yards, performing 360s or barrel rolls, collecting nitro bottles, using perfect and shockwave nitros, etc.

Win the race - I found I was able to win races even while being upwards of 150 points below the recommended rank. Always aim for the curved ramps to do barrel rolls, and always start your perfect nitro as soon as you start rolling. Whenever you go off normal ramps, start a 360 right as you leave the ramp and start your perfect turbo right as you start spinning. If you're right next to a car, you can either do a quick 360 to hit them or use nitro, either of which will knock them down. Drift around corners only when they're pretty sharp or you're going fast. Try to save your nitro for straight areas because your car automatically slows around corners so your nitro is pretty much wasted. Typically, the "high" path in a level is the faster and better one to take, but following nitro bottles is a good idea since it'll let you extend your nitro time. Never let your nitro meter fill up all the way without using it, otherwise you're wasting potential nitro you could be earning.

Escape - this is only for the "Hunted" levels, which can be a pain sometimes with the cops constantly slowing you down. There is one important tip here which is why I singled it out. In addition to what I mentioned above, always always save up your nitro until your meter is full. Cop cars are only destroyed readily by nitro shockwaves, so keep a full meter ready and whenever cops start to box you in or hit you, use your shockwave to destroy them. You'll find these levels are a piece of cake once you abuse shockwaves. Drift even when you don't need to in order to build up for another shockwave.

360s in one go - the only way to do this is to do a 360 right before going off a ramp so you continue spinning in the air. If you don't do this regularly already, get used to it since it, paired with a perfect nitro, can give you a long boost of speed.