1. Service history

If previous owner followed the schedule given by Proton and didn't bother topping up for better engine oil, it may have sludge issues which can lead to turbo failure. Can be dealt with by cleaning everything out but still not recommended since you dont know how long the owner has been driving the car under such condition for. Check other important things too like cooling system condition, warranty history (oil cooler hose, fan harness, cvt damper, etc.

2. Gearbox condition

Most people dont know how drive a car with CVT gently off the line, and with Punch it's worse since there's a engagement delay due to it being clutch based. Some proton foreman that dont know how to fill the gearbox fluid to the correct level, which can reduce lifespan even more. You need to bring someone experienced for this.
If you urgently need a car, might not be a good choice since it requires an in depth analysis as quite a few things can go wrong with this car.
Trying to keep this car in a tip top condition can break your wallet, and parts don't last as long as expected, which is normal for Proton's own stuff.. Their service cost comparison vs competitor cars don't take into account when things break or how long parts last for, which when taken into account can get really expensive.

And also take rattling sound into consideration.  My car have rattling sound everywhere until i have given up.

And also take rattling sound into consideration.  My car have rattling sound everywhere until i have given up.