There are 4 achievements regarding the number of runs you've made. You get them for 1, 10, 100, and 1000 runs. The fastest way to get 1000 runs is to play on "Two-way," choosing "Hard," and driving into the first car you see. Then retry and repeat. By the way, sometimes you get teleported into the air when you crash, so try to hit the edges of the cars to avoid that. But I recommend you play as long as possible, as you need a ton of money. Speaking of money...

There are 4 achievements regarding money. You need to have $1,000, $10,000, $100,000, and $1,000,000 in your bank account. I repeat, in your account. It doesn't count if you have spent a total amount of $1,000,000. There are only two ways of gaining money. One is fast and pricy, the other one is boring and tedious. You can spend 2€ on a DLC to get $200,000 (I don't know if you can repeat that multiple times) or you can just grind. There isn't another option.

There are 19 achievements for buying cars (I am not going to list them). You just need to buy the cars, that's it. I obviously recommend doing that after you got $1,000,000. There are 21 cars that you can buy, so you don't have to buy every single one (But why wouldn't you when you have a million dollars ;) ).

There are 4 achievements for playing every single game mode once. These include playing "One-way," "Two-way," "Time Attack," and "Speed Bomb." Play them once and you've got yourself 4 new achievements. And yes, the online mode isn't mandatory (Luckily, since no one plays it online anymore).

There are 4 achievements for playing the game on different difficulties. You need to play any mode (excluding online) on easy, normal, hard, and peaceful. Now, easy, normal, and hard are easy to get, but peaceful is another story. You need to play on "Time Attack" and wait for the timer to run out, then you get the achievement. You can also get it in "Speed Bomb." Just wait until the bomb explodes, and you're done.

You need to get 50k points on every game mode (excluding online again). But you have to do it on hard. That can be quite challenging, but after some time and skill, you'll be able to get it. There are only two tips I can give. On the track "G r i d" there are more cars, making it easier to hold and make combos. Because yes, combos are very important. You can make it without combos, it would just take very long. And then I have one tip for "Speed Bomb," since that is the hardest out of the three modes. If you change your perspective to "Bird's eye view", reaching 50k gets way easier because you can see more.

You can do this with any car. You need to buy a new paint, neon wheels, turbo, nitro, and police sirens. Apply these to your car and you get 5 new achievements.

Aaand that's it! Those are all the achievements in Retrowave. I hope I could help somebody :) If you have any questions or would like to add something that I missed, please let me know. Oh, and thanks for reading this guide! :D