telling
adjective /ˈtelɪŋ/
  /ˈtelɪŋ/
- having a strong or important effect; effective- a telling argument
- Although he didn’t score a goal, Tevez made a telling contribution to the game.
- These are telling points, but the argument is by no means over.
 
- showing effectively what somebody/something is really like, but often without intending to- The number of homeless people is a telling comment on the state of society.