General negative connotations:
* Troubled past: This is a neutral way to describe a past filled with difficulties.
* Dark history: This suggests a past filled with shameful or painful events.
* Chequered past: This implies a past with both good and bad aspects, but the bad outweighs the good.
* Blemished history: This implies a past that has been stained by wrongdoing or mistakes.
* Stained past: Similar to "blemished history," this emphasizes the negative impact of past actions.
* Tarnished reputation: This refers to a history that has caused damage to someone's standing.
More specific connotations:
* Criminal past: This refers specifically to a history of criminal activity.
* Scandalous past: This suggests a past filled with public controversy or wrongdoing.
* Shameful past: This implies a past that someone is deeply embarrassed about.
* Regrettable past: This refers to a past filled with actions that someone now regrets.
Figurative language:
* Haunted by the past: This suggests that someone is still burdened by their past.
* Shadowed by the past: This implies that someone's past continues to affect them negatively.
The best word will depend on the context and the specific meaning you want to convey.