Decisive (adjective)

Having the power or quality of deciding; producing a definite result.

Origin:

Late 16th century; from latin decisivus, from decidere "determine".

Examples:

1. The decisive victory was a turning point in the war.
2. The decisive factor was the quality of the product.
3. The decisive vote was cast by the chairman.
4. The decisive moment came when he made the speech.
5. The decisive action was taken after careful consideration.