very
dangerous
proverbial
He was on the proverbial slippery slope to bankruptcy.

go down, head down, slide down
This nation is sliding further down the slippery slope of repression.

lead sb down, take sb down
be on

argument
The slippery-slope argument can be used against anything.

slippery slope of
the slippery slope of moral relativism

slippery slope to
a slippery slope to divorce

slippery slope towards/toward

be the start of a slippery slope, be the top of a slippery slope
This is just the start of a slippery slope that ends with dictatorship.

Slippery-slope is used with these nouns:
argument