かんべん勘弁kanben
1.
The act of allowing someone to avoid consequences for their mistakes or shortcomings with a sense of leniency, often expressed as a request to stop or refrain from further discussion or demands.
2.
A way of indicating that one has reached their limit in tolerating persistent inquiries or unreasonable requests, conveying a subtle plea for the other party to cease their actions or demands.
3.
Acknowledgment of error or inconvenience, combined with an implication of forgiveness, typically used to soften a refusal or decline to further a discussion or negotiation.
Example:
同じことを何回繰り返すの。屋上屋を架すようなくどい説明は勘弁してよ。