During single-engine taxi, how is the asymmetric power compensated for?
First off, the thrust asymmetry problem is far less pronounced in large jet aircraft as compared with light twin engine propeller driven aircraft.  Secondly, taxi operations generally don’t use very much thrust, with the engines often at idle power during this process, only requiring brief bursts of moderate thrust to get the aircraft moving from standstill.

Taxiing small, light twins can be difficult in an OEI (One Engine Inoperative) scenario, in many cases being almost impossible to turn the airplane sharply toward the good engine.  Sometimes pilots will simply turn the aircraft only towards the dead engine and perform a 270° turn toward the dead engine instead of attempting to turn the airplane toward the good engine, should a turn toward the good engine be required.  Sometimes, as a loss of an engine becomes an emergency situation, a light twin pilot will sometime just shut down on the runway or on a turnoff, then just have the aircraft towed back as opposed to attempting to taxi it with an OEI. 

Asymmetric thrust can also be used by light twin aircraft to perform even sharper turns at slow speeds, with the pilot simply advancing the throttle to the engine on the outside of the turn while leaving the throttle on the inside of the turn at idle.  This can also be useful for maintaining directional control while taxiing, taking off and landing in strong crosswind conditions, since it requires less rudder input to correct.