HOT WHEELS UNLEASHED 2 - Turbocharged

Garage > Collection > Select vehicle/'Vehicle Management' > buy all 15 skills. All 15 have to be bought for the same vehicle.

You'll need 15⬆️ Skill Points, which will be most quickly earned on 'Hot Wheels Creature Rampage' ('career mode') - they are the white and blue up arrow tokens ⬆️. You can win multiple Skill Points after each event, so it probably won't take 15 events to earn them.
After 'The Octopus' (6th event) make sure you detour north after the orange 7th event 'A new challenge' and activate the fuscia challenge 'Genius of the class' (which will give you the 'Challenge accepted!'🏆 achi) and you should be awarded any remaining required Skill Points after the 12th event 'Middle road'.
You don't need to equip the skills - you can only equip 6 anyway*, so it's a bit of a silly achi. Also, only the three orange 'Obstacle' skills seem to be free of the pros and cons ('pro et contra' - Latin, meaning 'For and against' - I just looked it up 👍😸), so I equipped those first and used the vehicle to win more Skill Points.
It took me about 2 hours from scratch to get the 15 Skill Points and the achi using my spare Xbox account (or however long it takes to win the 12th career event 'Middle road').
You'll also need 1250 coins or 1🔧 Upgrade Kit (spanner/wrench🔧 token) to unlock the Powered tier skills, and 3000 coins or 2 Upgrade Kits to unlock the Ultimate tier - but you'll have those 4250 coins after 1 'career' event, and long before the 15 Skill Points, provided you haven't spent them.

*To get the 'Better too much'🏆 achi you first have to own or buy a duplicate vehicle (it will say "Already owned" beneath it in the shop), then buy and equip 4 (green) handling skills, which then adds 'Unrestrained Speed' as the free 7th skill. Alternatively, equip 4 (blue) boost skills to get 'Hyperboost' as the 7th skill. Then equip 2 skills from a different category.

NB: I had a problem with glitched achis due to progress not tracking (possibly caused by Quick Resume). I fixed it by going offline, via console 'Network settings'>'Go offline', then quickly losing an Elimination (Quick Mode) event, then going back online after seeing progress on the Xbox's achievement tracker.