General Negativity:
* Glib: Suggests a smooth, insincere way of talking.
* Slick: Similar to glib, but with an emphasis on being too smooth and artificial.
* Creepy: Implies something unsettling and disturbing.
* Unsavory: Suggests something morally questionable or unpleasant.
* Unctuous: Describes someone who is overly flattering and insincere.
Physical Descriptions:
* Viscous: For a thick, sticky substance.
* Gooey: For a sticky, soft substance.
* Mucous: For a slimy substance found in the body.
* Mucky: For something dirty and slimy.
Figurative Language:
* Devious: Suggests cunning and underhanded behavior.
* Duplicitous: Implies someone who is deceitful and two-faced.
* Cunning: Suggests cleverness, but often with negative connotations.
Other Options:
* Dishonest: Directly describes a lack of integrity.
* Unreliable: Implies someone who can't be trusted.
* Shady: Suggests something suspicious and potentially illegal.
Ultimately, the best word will depend on your specific meaning and the context of your writing.