I guess the worst car in pakistan in terms of bad fuel avg would be toyota vitz followed by all the corollas.
I am one of those guys on pakwheels who bring the best out of a car. Any car in good nick specially a Suzuki and honda could amaze you.
I have kept 2012 pkdm alto known for being fuel guzzler but i used to get 14+ avg inside islamabad. 2005 civic manual vti oriel used to give me 15+ in islamabad. Cultus 2018 used to give me 19+ inside islamabad and 8th gen civic 2011 civic gives me 14+.
It really depends on how good you have kept your car and how calmly you drive. If you drive like a maniac even a Prius wont save u