Power Drain

Power drain is a game mechanic used in Injustice Gods Among Us : Mobile.

Characters that use it
Nightwing/Prime and Nightwing/Regime - Nightwing is often refferred to as "king of power draining" due to him having the power drain on his first special.

Sinestro/Regime and Sinestro/Prime - Sinestro has power drain on his second special,except Sinestro/Green Lantern/Green Lantern

Green Arrow/Insurgency and Green Arrow/Arrow - Green Arrow also has his power drain on his first special.

All forms or variants of Lex Luthor have power drain on special 1.

Power-Immune Characters
Static/Prime,Lobo/Prime and Batman/Arkham Knight are immune to power drain. But you need to tap on it on the "Select Buffs" screen on Batman/Arkham Knight.

Blocking Gear
You can also reduce the effect of the power drain with blocking gear.