Efficient and quick charging and discharging of a 2.7V supercapacitor with a 4.2V Li-ion battery
If you want to charge the capacitor quickly, but not overcharge it, then just use a large power FET and a comparator that turns it off if the capacitor is > 2.7 V.

However, if you don't limit the current, it will be many (say 10) A, and the power in the FET will be ~ 1.3V*10=13 W. It will take 13 s to charge the capacitor, and the FET would need a heatsink. Therefore I suggest that you do add a series resistance.