We were charged more than double what we expected we would need to pay.
We booked the option to have a second driver through rentalcars.com and therefore thought it was included in the price but we got charged for it again by Europcar.
Also we did not get the small car we wanted (Toyota Aygo) but an "upgrade" which was just a car that needed to be in the country we ended our holidays. A car that needs to be brought back to its home country is totally fine, but not the huge model (Toyota Avensis) we got instead of what we booked.
They told us to not hand in the car with full fuel because the fee for fuel there would be cheaper than what we would pay for it (because they have a deal with gas stations which made sense for us at the time). That was definitely not true, since we had to pay about 50 EUR for 20 liters of standard gas.
Also there were additional 30 EUR for taxes from Europcar on top of what was stated that the fees for gas, one-way and additional driver would be costing.
When we complained when we brought the car back the guy just told us "I can not do anything about it, that is how it works".
We looked at everything very closely and read the contracts at the counter but because of the explanations we got there and the additional deposit it is very unclear what you actually need to pay in the end.