Very poor quality, causing objections.

I've seen bad grammar, but this takes the biscuit.

She's been opening my letters – that really takes the biscuit.

Excellent, remarkable (in a positive sense).

Examples:

Thanks! You guys take the cake.

Once the party was over, everyone agreed that Elizabeth and her Harriet Tubman getup had taken the cake.

Idioms: Take the Biscuit (UK) / Take the Cake (US)