Asphalt Legends Unite

The description may sound a little confusing at first here. Each car has four items that can be upgraded:

1. Acceleration
2. Top Speed
3. Handling
4. Nitro

Each one of these categories is upgraded in stages for that car. They all start at stage 1, and each time you buy an upgrade it goes up one stage. So for this achievement, you need to purchase 100 upgrades total across all cars.

This will happen very early in the game. Initially with any car, you'll only be able to upgrade each category to stage 4 or 5 depending on the class, but that's 20 or 25 stage upgrades just for that one car. Considering you'll be upgrading at least 15-20 cars fully just at their base state (let alone after you star them up), this achievement is unavoidable and will unlock very early as you progress through Career Mode.