clincher
noun /ˈklɪntʃə(r)/
/ˈklɪntʃər/
[usually singular] (informal)- a fact, a remark or an event that settles an argument, a decision or a competition
- There was a lot of circumstantial evidence but they still needed a clincher, something cast iron that would carry a conviction.
- Sixsmith scored the clincher (= the winning goal) after 81 minutes.