the.com/weakest link

The one teammate whose mistakes you'll remember longer than the group's wins.

means The person or part in a chain of people/processes whose poor performance determines the failure point of the whole system.

from Rooted in the literal mechanics of a chain: a chain is only as strong as its weakest link, a proverb-like truth about metalwork known for centuries. The phrase jumped into everyday English as a general metaphor for group or system failure, but it exploded into pop culture via the early-2000s British TV game show 'The Weakest Link,' where contestants voted off the poorest performer each round — cementing the phrase as shorthand for 'the one dragging everyone else down.'

origin
From the chain metaphor: strength equals weakest point
pop culture
Became a gameshow where losers got voted off coldly
irony
Teams often cut skilled players just for being unlikeable
workplace use
Usually whispered, never said in the actual meeting
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