The Meaning of Condign
That which is ‘condign’ supposes an equal and proportionate relationship between service or effort (input) and return or results (output).
Condign praise is something that is completely apposite, ‘spot on’.
Condign criticism is well-grounded, truthful, compelling.
Condign service is that which meets a need perfectly.
‘Capriciously… the word condign is used…in connection with the word punishment. These and other words, if unlocked from their absurd imprisonment, would become extensively useful. We should say, for instance, ‘condign honours’, ‘condign reward’, ‘condign treatment’.
Thomas De Quincey, The Templars’ Dialogues in Wks IV 188 note