This note investigates a unified finite-time output feedback control strategy for a class of planar switched systems with an asymmetric output constraint. A fraction-type asymmetric barrier Lyapunov function (BLF) is constructed firstly. Based on relaxed assumptions on system nonlinearities together with the developed BLF, a set of finite-time state feedback controllers are designed systematically by revamping the technique of adding a power integrator. By incorporating the state controllers with switched reduced-order observers developed delicately, the task of finite-time stabilization for planar switched systems can be realized by the resultant output feedback controllers in consideration of asymmetric output constraints imposed on switched systems simultaneously. The proposed method enjoys the unification property such that it is workable for the scenarios of constrained and unconstrained cases, without the need of changing/redesigning the structures of controllers and observers. Finally, simulation results are presented to verify the proposed scheme.