Engines with lack bottom end power?

Is underpowered and soft being interchanged.

To me,

An underpowered engines is a stock low power peak hp around 4000-4500 rpm with an off idle-5000 rpm useable range obviously the larger the engine more torque idle-4500 rpm so will have more hp idle-4500 rpm. These all can be considered underpowered and obviously the smaller ones will be more underpowered in comparison.

I wouldn't think of soft bottom end as underpowered more as the engine doesn't want to operate down low and struggles to transition for low rpm into it's powerband without gearing and stall etc..