untrustworthier

In the May 1995 Word Ways, Darryl Francis gave examples of words having every numerical score from 1 (a) to 248 (superstitiously), and challenged readers to come up with a word scoring 249. Leonard Gordon suggested pyknodysostotics, pericardiomediastinitis, electroencephalographers, hexanitrodiphenylamine, hyperprothrombinaemia, photoroentgenographic, mercaptobenzothiazole and chemopallidothalamectomy, all but the first and last in Webster's Second or Third or inferrable from it. Richard Sabey noted superinstitution in Webster's Second. Susan Thorpe added inauthoritativeness, reconstructiveness and photosynthesizing from the OED. Sir Jeremy Morse suggested zoophysiologists (inferred from the Funk & Wagnalls unabridged word zoophysiology) and the inferred word untrustworthier.

[1995 August, “Extending Francis”, in Word Ways, volume 28, number 3, page 151

Who is sneakier, untrustworthier, and all round more devious that the newest oxymoron, the "Clinton Justice Department"?

1999 January 26, Docky Wocky [pseudonym], “Big Brother loses one”, in alt.current-events.clinton (Usenet)

On the day he wrote it William was in ‘a low, desponding, and queer state’. ‘I can’t describe my feelings,’ he said, but he had suicide in mind. The sharp instrument was ready for that purpose. ‘I did feel certain that the Devil would come to me that night’, he recalled, but there was no untrustworthier master than the Devil, and he failed to appear and claim his soul.

2005, Owen Davies, “Dove in the dock”, in Murder, Magic, Madness: The Victorian Trials of Dove and the Wizard, London; New York, N.Y.: Routledge, published 2014, →ISBN, page 103

In the old Cambodian culture before the Khmer Rouge regime, most men had as many wives as they could support. The more power and money they had, the untrustworthier they became.

2005, Vatey Seng, “Our Drifting Destination”, in The Price We Paid: A Life Experience in the Khmer Rouge Regime, Cambodia, Lincoln, Neb.: iUniverse, →ISBN, page 58

Morphological comparatives are exceedingly rare with adjectives that have four or more syllables, but note the case of untrustworthier.

[2008 November, Martin Hilpert, “The English comparative – language structure and language use”, in English Language and Linguistics, volume 12, number 3, Cambridge University Press, page 398