modified
traitorously, treacherously, deceitfully, faithlessly, falseheartedly, behind one's back, disloyally, underhandedly, basely, unfaithfully, perfidiously, dishonestly, erroneously, fallaciously, wrongly, incorrectly, unjustly, unscrupulously, roguishly, knavishly, under the garb of, hypocritically, insincerely, dishonorably, crookedly*.
Antonyms truly*, justly*, honorably.
