decisive

adj

1.
determining or having the power to determine an outcome
Antonym:
indecisive
Derived from:
decide decisiveness
2.
unmistakable
Derived from:
decisiveness
3.
characterized by decision and firmness
Antonym:
indecisive
Derived from:
decide decisiveness
4.
forming or having the nature of a turning point or crisis
critical
Derived from:
decisiveness