unduly Definition

1a. Unjustifiable; improper;
1b. Inappropriately or unjustifiably great; excessive.

Example: undue criticism
Thesaurus: undeserved, disproportionate, overmuch, uncalled-for, extravagant, immoderate, needless, excessive, unwarranted, inordinate, intemperate; Antonym: reasonable.
2. rare
Said of a debt, etc: not due or owing.

Unjustifiably.

Excessively; unreasonably.
Thesaurus: unnecessarily, immoderately, inordinately, extravagantly, overly, disproportionately, overmuch; Antonym: reasonably.