A slippery slope.

Meaning

A course of action that seems to lead inevitably to a negative outcome.

Examples

• John: 'Relaxing these rules could be a <b>slippery slope</b> to complete chaos.'
• Alice: 'I agree, we need to be cautious about unintended consequences.'
• John: 'That's a valid concern; we need to consider all aspects carefully.'
• Alice: 'Lowering the drinking age could be a <b>slippery slope</b> towards increased alcohol abuse.'